THE   CHEMISTRY 

AND 

TECHNOLOGY   OF    PAINTS 


BY  MAXIMILIAN  TOCH 

AUTHOR  OF   "MATERIALS  FOR  PERMANENT  PAINTING,"   ETC.,   ETC, 


SECOND  REVISED  EDITION 


NEW  YORK 

D.   VAN  NOSTRAND   COMPANY 
1916 


COPYRIGHT,  1907,  BY 
D.  VAN  NOSTRAND  COMPANY 

COPYRIGHT,  IQl6,  BY 
D.  VAN  NOSTRAND  COMPANY 


THE -PLIMPTON -PRESS 
NORWOOD  -MASS-  U-S'A 


PREFACE   TO   FIRST  EDITION 

THE  difficulty  which  I  encountered  in  writing  this 
book  was  not  how  much  to  write  but  how  much  to  omit, 
for  I  found  on  compiling  my  notes  that  I  could  very 
easily  have  made  two  volumes,  each  larger  than  the 
present  one,  and  still  would  not  have  covered  the  ground 
thoroughly.  It  is  for  this  reason  that  I  have  omitted 
many  of  the  pigments  which  are  rarely  used,  and  have 
paid  no  attention  whatever  to  the  pigments  which  have 
gone  out  of  use. 

I  have  not  considered  it  desirable  to  use  any  space  in 
this  book  with  extended  repetition  of  matter  that  can  be 
found  in  other  books  of  reference,  for  I  have  so  much 
matter  which  is  the  result  of  original  research  that  very 
few  references  are  cited. 

This  being  the  first  book  ever  written  on  the  subject 
of  mixed  paints,  I  am  cognizant  of  the  fact  that  there 
are  many  matters  in  it  which  I  shall  have  to  alter  in 
future  editions,  and  many  subjects  upon  which  I  shall 
have  to  enlarge.  It  must  be  borne  in  mind  that  mixed 
paint  is  demanded  by  a  progressive  civilization  and  that 
there  are  no  two  manufacturers  who  make  identically  the 
same  mixtures.  As  time  changes,  the  progressive  manu- 
facturer alters  his  formulas,  and  an  indication  of  this  is 
that  the  original  mixed  paints  were  mostly  emulsions 
and  soap  solutions,  whereas  today  the  tendency  is  toward 
purity  and  improvement,  and  one  manufacturer  tries  to 
outdo  the  other  in  making  a  paint  that  will  last,  the 
ideal  pa^int,  however,  being  never  reached. 

3 


3411G1 


4  PREFACE   TO  FIRST  EDITION 

This  volume  is  intended  for  the  student  in  chemistry 
who  desires  to  familiarize  himself  with  paint,  or  the 
engineer  who  desires  a  better  knowledge  of  the  subject, 
or  for  the  paint  manufacturer  and  paint  chemist  as  a 
work  of  reference.  It  is  not  intended  for  those  who  have 
no  previous  knowledge  or  training  in  the  subject. 

Some  of  the  chapters  in  this  book  are  taken  from  my 
lectures  delivered  at  various  universities,  and  others  are 
extracts  from  lectures  delivered  before  scientific  bodies. 
One  of  the  objects  which  I  have  had  in  view  during  the 
entire  time  I  have  been  writing  this  book  is  to  familiarize 
the  student  in  chemistry,  or  the  post-graduate,  with  the 
science  and  technology  of  modern  paints,  so  that  in  a 
very  short  time  the  chemist  unfamiliar  with  the  subject 
may  obtain  sufficient  knowledge  to  make  a  reasonable 
examination  of  paint. 

The  chapter  on  linseed  oil  illustrates  this,  and  my 
researches  and  theories  on  the  difference  between  raw 
and  boiled  linseed  oil  are  here  published  for  the  first  time. 
From  the  formulas  and  disquisition  on  the  subject  it 
can  be  easily  seen  that  if  raw  linseed  oil  be  taken  as  a 
standard  nearly  all  comparisons  fail  if  boiled  linseed  oil 
is  under  examination. 


320  FIFTH  AVENUE 
NEW  YORK,  1907 


PREFACE   TO    SECOND    EDITION 

SINCE  the  first  edition  of  this  book  was  published  the 
efforts  of  a  large  number  of  technical  men  working  in  this 
field  have  resulted  in  very  important  advances  both  in  the 
production  of  new  pigments,  oils  and  special  paints  and  in 
the  scientific  elucidation  of  many  obscure  phenomena  in 
paint  technology.  Improvements  have  also  been  made  in 
the  method  of  manufacture  as  well  as  in  the  quality  of 
many  of  the  older  pigments.  Advances  have  also  been 
made  in  the  discovery  and  utilization  of  a  number  of  oils 
which  have  not  heretofore  found  extended  use  in  the  paint 
trade. 

These  important  advances  have  necessitated  rewriting 
most  of  the  book  and  the  addition  of  new  matter  to  the  ex- 
tent of  doubling  its  size.  Some  of  the  important  additions 
which  may  be  worthy  of  mention  are,  standard  specifica- 
tions for  pigments  and  oils;  new  special  paints  and  driers; 
the  theory  of  corrosion  of  iron  and  steel  and  its  prevention 
as  well  as  the  action  of  fungi  on  paints;  the  important  sub- 
ject of  the  hygiene  of  workmen;  detailed  methods  of  analy- 
sis of  paints  and  paint  materials  as  well  as  tables  of 
constants  of  such  materials. 

Undoubtedly  the  chemical  manufacturer  and  the  chemical 
student  who  intends  to  become  proficient  in  paint  chemistry 
will  find  it  essential  to  read  a  great  deal  of  the  past  as  well 
as  the  current  technical  literature  of  the  subject,  but  it  is 
the  hope  of  the  author  that  this  book  will  give  the  student 
a  comprehensive  survey  of  the  progress  already  made  and 
furnish  a  foundation  for  further  improvement. 

MAXIMILIAN  TOCH 

320  FIFTH  AVENUE 
NEW  YORK 
July,  1916  s 


CONTENTS 

PREFACE  TO  FIRST  EDITION 3 

PREFACE  TO  SECOND  EDITION 5 

INTRODUCTION 13 

CHAPTER  I 
THE  MANUFACTURE  OF  MIXED  PAINTS 18 

CHAPTER  II 

THE  WHITE  PIGMENTS 26 

White  Lead.  —  Sulphate  of  Lead.  —  Sublimed  White  Lead.  — 
Standard  Zinc  Lead  White.  —  Ozark  White.  —  Zinc  Oxid.  — 
Zinox.  —  Lithopone. 

CHAPTER  III 

THE  OXIDS  OF  LEAD 53 

Litharge.  —  Red  Lead.  —  Blue  Lead. 

CHAPTER  IV 

THE  RED  PIGMENTS 62 

Venetian  Reds.  —  Indian  Red.  —  Permanent  Vermilion.  —  Helio 
Fast  Red.  —  Lithol  Red. 

CHAPTER  V 

THE  BROWN  PIGMENTS 71 

American  Burnt  Sienna.  —  Italian  Burnt  Sienna.  —  Burnt  Umber. 

—  Burnt  Ochre.  —  Prince's  Metallic  or  Princess  Mineral  Brown. 

—  Vandyke  Brown. 


8  CONTENTS 

CHAPTER  VI 

THE  YELLOW  PIGMENTS 78 

American  Yellow  Ochre.  —  French  Yellow  Ochre.  —  Chrome  Yel- 
low. —  Chromate  of  Zinc. 

CHAPTER  VII 

THE  BLUE  PIGMENTS 84 

Ultramarine  Blue.  —  Artificial  Cobalt  Blue.  —  Prussian  Blue. 

CHAPTER  VIII 

THE  GREEN  PIGMENTS  . 92 

Chrome  Green.  —  Chromium  Oxid.  —  Green  Aniline-  Lakes.  — 
Zinc  Green.  —  Verte  Antique  (Copper  Green). 

CHAPTER  IX 

THE  BLACK  PIGMENTS 97 

Lampblack.  —  Carbon  Black. — -Graphite. —  Charcoal.  —  Vine  Black. 
—  Coal.  —  Ivory  Black.  —  Drop  Black.  —  Black  Toner.  — 
Benzol  Black.  —  Acetylene  Black.  —  Mineral  Black. 

CHAPTER  X 

THE  INERT  FILLERS  AND  EXTENDERS no 

Barytes.  —  Artificial  Barium  Sulphate.  —  Barium  Carbonate.  — 
Silica.  —  Infusorial  Earth.  —  Kieselguhr.  —  Fuller's  Earth.  — 
Clay.  —  Asbestine.  —  Asbestos.  —  Calcium  Carbonate.  —  White 
Mineral  Primer.  —  Marble  Dust.  —  Spanish  White. —  Artificial 
Calcium  Carbonate.  —  Gypsum. 

CHAPTER  XI 
MIXED  PAINTS 140 

Anti-fouling  and  Ship's  Bottom  Paints.  —  Concrete  or  Portland 
Cement  Paints.  —  Paint  Containing  Portland  Cement.  —  Damp- 
Resisting  Paints.  — Enamel  Paints.  —  Flat  Wall  Paints.  —  Floor 
Paints.  —  Shingle  Stain  and  Shingle  Paint. 

CHAPTER  XII 
LINSEED  OIL 158 

Linseed  Oil.  — -  Standard  Specifications,  American  Society  for  Testing 
Materials  for  Linseed  Oil.  —  U.  S.  Navy  Department  Specifica- 
tions for  Linseed  Oil.  —  Stand  Oil.  —  Japanner's  Prussian  Brown 
Oil. 


CONTENTS  9 

CHAPTER  XIII 

CHINESE  WOOD  OIL 180 

Chinese  Wood  Oil  —  A  Method  for  the  Detection  of  Adulteration 
of  China  Wood  Oils.  —  Standard  Specifications  American  Society 
for  Testing  Materials  for  Purity  of  Raw  Chinese  Wood  Oil. 

CHAPTER   XIV 
SOYA  BEAN  OIL '.'.'. 192 

CHAPTER  XV 
FISH  OIL 203 

CHAPTER  XVI 

MISCELLANEOUS  OILS 210 

Herring  Oil.  —  Corn  Oil. 

CHAPTER  XVII 

TURPENTINE 217 

Turpentine.  —  Wood  Turpentine.  —  Standard  Specifications  Ameri- 
can Society  for  Testing  Materials  for  Turpentine.  —  U.  S.  Navy 
Department  Specifications  for  Turpentine. 

CHAPTER   XVIII 
PINE  OIL 228 

CHAPTER  XIX 
BENZINE 238 

CHAPTER   XX 

TURPENTINE  SUBSTITUTES 243 

Benzol.  — •  Toluol.  —  Xylol.  —  Solvent   Naphtha. 

CHAPTER  XXI 

COBALT  DRIERS 247 


I0  CONTENTS 

CHAPTER  XXII 

COMBINING  MEDIUMS  AND  WATER  . 254 

Combining  Mediums.  —  Water  in  the  Composition  of  Mixed  Paints. 

CHAPTER  XXIII 
FINE  GRINDING 2S9 

CHAPTER  XXIV 
THE  INFLUENCE  OF  SUNLIGHT  ON  PAINTS  AND  VARNISHES   ....     261 

CHAPTER  XXV 

PAINT  VEHICLES  AS  PROTECTIVE  AGENTS  AGAINST  CORROSION     .    .    .     266 

CHAPTER  XXVI 
THE  ELECTROLYTIC  CORROSION  OF  STRUCTURAL  STEEL 276 

CHAPTER  XXVII 
PAINTERS'  HYGIENE 281 

CHAPTER  XXVIII 

THE  GROWTH  OF  FUNGI  ON  PAINT 284 

ANALYSIS  OF  PAINT  MATERIALS 288 

White  Lead.  —  Basic  Lead  Sulphate.  —  Zinc  Lead.  —  Zinc  Oxid.  — 
Lithopone.  —  Red  Lead  and  Orange  Mineral.  —  Iron  Oxids.  — 
Umbers  and  Siennas.  —  Mercury  Vermilion.  —  Chrome  Yellows 
and  Oranges.  —  Chrome  Greens.  —  Prussian  Blue.  —  Ultra- 
marine. —  Black  Pigments.  —  Graphite.  —  Blanc  Fixe.  - 
Whiting.  —  Gypsum  or  Calcium  Sulphate.  —  Silica.  —  Asbes- 
tine. —  Clay.  —  Barytes.  —  Barium  Carbonate.  —  Mixed 
White  Paints.  --  White  Pigments.  --  Paints.  --  Rosin.  — 
Rosin  Oils.  —  Oils.  —  Etc.,  Etc. 


CONTENTS 


APPENDIX 

SOME  CHARACTERISTICS  AND  VARIABLES  OF   COMMERCIAL   BOILED 

OILS 343 

CHARACTERISTICS  OF  BOILED  OILS  (LEWKOWITSCH) 343 

CONVERSION  OF  FRENCH  (METRIC)  INTO  ENGLISH  MEASURE.    .    .  344 

CONVERSION  OF  FRENCH  (METRIC)  INTO  ENGLISH  WEIGHT    .    .    .  344 

METRIC  SYSTEM  OF  WEIGHTS  AND  MEASURES 345 

SPECIFIC  GRAVITY  OF  VARIOUS  MATERIALS 346 

SPECIFIC  GRAVITY  OF  THE  ELEMENTS 350 

POUNDS  OF  OIL  REQUIRED  FOR  GRINDING   100  POUNDS  VARIOUS 

DRY  PIGMENTS  INTO  AVERAGE  PASTES 350 

SPECIFIC  GRAVITY  OF  VARIOUS  WOODS 351 

TABLE  SHOWING  THE  COMPARISON  OF  THE   READINGS  OF  THER- 
MOMETERS    352 

INTERNATIONAL  ATOMIC  WEIGHTS 353 

LIST  OF  PHOTOMICROGRAPHS 355 

INDEX 357 


THE    CHEMISTRY 


AND 


TECHNOLOGY  OF   PAINTS 


THE  manufacture  of  mixed  paints  is  essentially 
American,  having  been  accredited  to  some  enterprising 
New  Englanders  who  observed  that  when  a  linseed  oil 
paint  was  mixed  with  a  solution  of  silicate  of  soda  (water 
glass)  an  emulsion  was  formed,  and  the  paint  so  made 
showed  very  little  tendency  to  settle  or  harden  in  the 
package.  Several  lay  claim  to  this  discovery.  The 
first  mixed  paint  was  marketed  in  small  packages  for 
home  consumption  and  appeared  about  1865. 

The  addition  of  silicate  of  soda  is  still  practised  by  a 
few  manufacturers,  but  the  tendency  is  to  eliminate  it 
as  far  as  possible  and  to  minimize  as  much  as  possible 
the  use  of  an  alkaline  watery  solution  to  keep  the  paint 
in  suspension.  The  general  use  of  zinc  oxid  has  had 
much  to  do  with  the  progress  of  mixed  paint,  for  it  is 
well  known  that  corroded  white  lead  and  linseed  oil 
settle  quickly  in  the  package,  while  zinc  oxid  keeps  the 
heavier  lead  longer  in  suspension.  Where  only  heavy 
materials  are  used,  manufacturers  are  inclined  to  add 
up  to  4  per  cent  of  water.  Under  another  chapter  on 
"Water  in  the  Composition  of  Mixed  Paints,"  page  254, 
this  subject  will  be  fully  discussed. 

To  the  pigments  are  added  many  materials  possessing 
but  little  body,  hiding  or  covering  property,  which  are 

13 


14  INTRODUCTION 

known  as  inert  fillers,  and  some  of  these,  particularly 
the  silicates  of  alumina  and  the  silicates  of  magnesia, 
the  various  calcium  carbonates,  and  silica  itself,  are  used 
to  counterbalance  the  heavy  weight  or  the  specific  gravity 
of  the  metallic  pigments;  and  whereas  these  inert  fillers 
were  formerly  regarded  as  adulterants  and  cheapening 
agents,  they  are  now  looked  upon  as  necessities,  and  the 
consensus  of  opinion  among  practical  and  many  scientific 
investigators  is  that  a  compound  paint  composed  of  lead, 
zinc,  and  a  tinting  pigment,  to  which  an  inert  material 
has  been  added,  is  far  more  durable  than  paint  made  of 
an  undiluted  pigment.  The  consuming  public  and  the 
painter  himself  have  not  been  sufficiently  educated  as  yet 
to  understand  the  merits  of  these  diluents,  and  the  paint 
manufacturer  has  been  reticent  in  his  statements  regard- 
ing the  use  of  various  fillers. 

These  facts  account  to  a  large  degree  for  the  opposi- 
tion to  the  use  of  such  materials.  When  it  is  taken 
into  consideration  that  within  forty  years  the  sale  of 
mixed  paints  in  the  United  States  has  grown  to  almost 
sixty  million  gallons  per  year  (and  the  outlook  is  for  a 
larger  increase  in  the  use  of  mixed  paints),  it  is  obvious 
that  the  demand  is  healthy,  even  though  the  manufacture 
of  mixed  paints  has  been  directed  or  based  largely  upon 
empirical  formulas. 

One  of  the  railroads  of  the  United  States  buys  at  this 
writing  upward  of  one  million  dollars'  worth  of  paint 
material  per  year,  a  large  share  of  this  being  mixed  paints, 
or  paint  ready  for  the  brush.  Nearly  all  of  the  large 
manufacturing  industries  which  use  large  quantities  of 
paint  are  gradually  altering  their  methods,  so  that  their 
paint  comes  to  them  ready  for  application.  In  no  case, 
to  the  best  knowledge  of  the  author,  does  a  single  one 
of  these  industries  prescribe  a  single  pigment  with  linseed 


INTRODUCTION  15 

oil  for  general  purposes,  for  it  has  been  shown  that  a 
mixture  of  several  pigments  and  a  filler  is  superior  from 
the  standpoint  of  lasting  quality  and  ease  of  application 
to  a  mixture  of  a  single  strong  pigment  and  the  vehicle. 

The  structural  iron  industry,  which  has  reached  an 
enormous  development  in  the  United  States,  uses  paints 
ready  mixed  with  the  one  exception  of  red  lead,  which,  in 
the  old  prescription  of  thirty-three  pounds  of  red  lead  to 
one  gallon  of  oil,  cannot  be  prepared  ready  for  the  brush, 
for  reasons  which  will  appear  in  the  proper  chapter. 

The  manufacture  of  agricultural  implements,  wagons, 
and  wire  screens  can  be  cited  as  industries  in  which  manu- 
facturers have  within  a  very  few  years  adopted  the  use 
of  ready-mixed  paints  for  their  products.  These  paints 
are  not  brushed  on,  but  are  so  scientifically  made,  and 
the  relation  between  a  vehicle  and  a  pigment  is  so 
carefully  observed,  that  large  pieces  of  their  products  can 
be  dipped  into  troughs  and  the  paint  allowed  to  drain. 
The  surface  is  more  evenly  coated  and  the  wrork  done  in 
far  less  time  than  would  be  required  were  it  applied 
by  means  of  the  brush,  as  in  former  years. 

In  view  of  all  these  facts,  the  prejudice  on  the  part 
of  the  general  public  and  the  trepidation  of  the  manu- 
facturer are  to  blame  for  the  unheralded  knowledge  of 
the  constituents  of  mixed  paints.  There  are  many  cases 
where  materials  which  were  once  despised  are  regarded 
now  as  essential  to  the  life  and  working  quality  of  paint, 
and  the  attitude  of  the  paint  manufacturer  must  in 
the  future  be  a  frank  and  open  admission  of  the  com- 
position of  his  materials.  If  a  paint  is  composed  of  a 
mixture  of  white  lead,  zinc  oxid,  and  barytes,  and  it  has 
been  proved  that  a  mixture  of  these  three  will  outlast 
a  mixture  of  either  of  the  other  two,  there  is  no  reason 
why  a  manufacturer  of  mixed  paints  shall  not  so  state. 


!6  INTRODUCTION 

New  materials  have  come  into  use  which  have  taken 
the  place  in  a  large  degree  for  many  purposes  of  the 
time-honored  and  useful  white  lead,  and  many  mixed 
paint  manufacturers  have  already  begun  to  educate  the 
public  to  the  superiority  of  one  material  over  another. 
It  stands  to  reason,  however,  that  the  manufacturer  of 
a  raw  material  which  has  been  in  use  for  a  very  long 
time  is  going  to  refute  as  much  as  possible  the  statement 
made  writh  regard  to  newer  materials,  and  these  dis- 
cussions tend  to  do  good  rather  than  harm. 

In  the  case  of  one  of  the  large  railroads,  the  speci- 
fications for  a  certain  paint  demand  the  use  of  over  70 
per  cent  of  inert  filler,  and  if  these  inert  fillers  had  no 
merit  no  railroad  or  large  corporation  would  permit  their 
use.  These  large  corporations  support  chemical  labora- 
tories and  employ  the  best  talent  which  they  can  engage. 
They  continually  experiment,  and  in  their  specifications 
the  results  of  their  experiments  are  obvious,  and  there- 
fore if  a  large  corporation  can  state  publicly  not  only 
what  the  composition  of  these  paints  shall  be,  but  con- 
clude that  such  compositions  are  based  upon  the  results 
of  scientific  investigation,  the  paint  manufacturer  can 
do  likewise  and  stand  back  of  his  products,  provided  they 
be  mixtures  of  various  materials  which  time,  science, 
and  investigation  have  proved  to  be  superior. 

Unfortunately,  however,  there  are  some  manufactur- 
ers who  have  "hidden  behind  a  play  of  words"  and  per- 
mit chicanery  and  finesse  to  enter  into  the  description 
of  their  products;  but  fortunately  some  of  them  have 
seen  the  errors  of  their  way,  and  already  there  is  a  ten- 
dency toward  openness  and  candor  with  regard  to  their 
wares.  There  was  a  time,  and  it  still  exists  in  a  measure, 
when  substitutes  for  white  lead  were  very  largely  sold, 
and  misleading  labels  appeared  on  the  packages;  for 


INTRODUCTION  17 

instance,  a  man  would  make  a  mixture  of  80  per  cent 
barytes  and  20  per  cent  white  lead,  and  would  print 
on  the  label — "The  lead  in  this  package  is  guaranteed 
absolutely  pure,"  followed  by  a  commendation  and 
guarantee  that  certain  sums  of  money  would  be  paid  if 
the  lead  were  not  found  to  be  pure.  This,  of  course,  is 
a  moral  fraud  and  an  unfortunate  play  on  the  ambiguity 
of  the  language,  and  many  of  the  manufacturers,  in  view 
of  such  unfortunate  misstatements,  are  altering  the 
names  of  their  paste  products,  or  lead  substitutes, 
omitting  the  word  "lead"  entirely. 

Another  unfortunate  mistake  is  made  when  a  manu- 
facturer makes  a  mixed  paint  and  states  on  the  label, 
"This  paint  is  composed  of  pure  lead,  pure  zinc,  pure 
linseed  oil,  pure  drier,  and  nothing  else."  The  analyses 
of  the  paint  have  proved  that  in  addition  to  the  "pure" 
products  mentioned  three  gallons  of  water  were  added 
to  every  hundred  gallons  of  paint  in  order  to  keep  the 
paint  in  suspension,  and  that  it  had  not  been  strained 
and  therefore  contained  a  large  amount  of  dirt  and  for- 
eign matter.  Ethics  would  clearly  indicate  that  no 
manufacturer  has  a  moral  right  to  label  his  paint  as 
being  entirely  pure  and  composed  of  four  materials, 
when  as  a  matter  of  fact  an  excessive  quantity  of  water 
was  added  which  destroyed  in  a  large  degree  the  value 
of  the  other  materials.  In  another  chapter  the  question 
of  the  percentage  of  water  which  may  be  contained  in 
any  paint  will  be  thoroughly  discussed.  Three  per  cent 
is  entirely  excessive  in  an  exterior  linseed  oil  paint,  and 
a  manufacturer  has  no  right,  either  morally  or  legally, 
to  hide  behind  a  misrepresentation  of  his  paint  when 
the  paint  is  largely  adulterated  for  the  purpose  of  over- 
coming his  ignorance  in  the  manufacture. 


CHAPTER  I 
THE  MANUFACTURE  OF  MIXED  PAINTS 

THE  modern  methods  of  making  mixed  paint  are 
divided  into  two  classes,  which  depend  upon  the  specific 
gravity  and  fineness  of  the  raw  material. 

One  of  the  methods  employed  is  to  mix  the  raw 
material  with  sufficient  linseed  oil  to  form  a  very  heavy 
paste,  the  proper  tinting  material  being  added  during 
the  process  of  mixing.  This  paste  is  then  led  down 
from  the  floor  on  which  it  is  made  into  a  stone  mill  and 
ground.  Even  when  the  mill  is  water-cooled,  the  mass 
frequently  revolves  at  such  a  speed  that  the  paste  paint 
becomes  hot.  It  is  then  allowed  to  run  from  the  mill 
into  a  trough  called  the  "cooler,"  or  is  stored  in  barrels 
to  be  thinned  at  some  later  time.  In  case  the  operation 
is  continuous  and  the  paste  is  thinned  at  once,  it  passes 
from  a  stone  mill  to  a  mixer  below  which  contains  the 
requisite  quantity  of  thinning  material  composed  of  oil, 
volatile  thinner,  and  drier,  where  it  is  intimately  mixed 
by  means  of  paddles.  It  is  then  compared  with  the 
standard  for  shade,  and  if  the  tone  should  not  be  identical 
with  the  former  mixing,  either  tinting  material  or  pigment 
is  added  in  sufficient  amount  to  produce  the  proper 
shade.  From  the  last  mixer,  known1  as  the  "liquid 
mixer,"  the  paint  is  drawn  off  and  filled  into  packages, 
the  final  operation  before  allowing  it  to  enter  the  package 
being  to  strain  it.  This  method  has  been  used  ever 
since  mixed  paints  have  been  made.  The  majority  of 

18 


THE  MANUFACTURE  OF  MIXED  PAINTS  19 

white  paints,  or  paints  of  heavy  specific  gravity,  are 
made  in  this  manner. 

The  paints  of  lower  specific  gravity,  varnish  and 
floor  paints,  are  made  differently.  This  method  is  really 
the  reverse  of  the  old-fashioned  method,  in  that  the 
liquid  and  pigment  are  placed  in  a  mixer  on  an  upper 
floor  in  the  amounts  necessary  to  produce  the  correct 
consistency.  The  paint  is  run  down  in  a  thin  stream  to 
the  floor  below  into  a  mill  known  as  the  "liquid  mill." 
The  liquid  mills  revolve  very  rapidly,  the  stones  being 
flat. 

According  to  the  best  practice  of  making  paste 
paints  a  grinding  surface  is  supposed  to  be  conical, 
although  there  is  much  difference  of  opinion  on  this 
subject.  When  the  paint  has  run  through  the  stones  of 
a  liquid  mill,  it  comes  out  of  a  spout  and  is  then  ready 
for  packing,  due  precaution  being  taken,  however,  to 
strain  it  twice,  once  as  it  passes  down  into  the  liquid 
mill  and  again  as  it  flows  out.  There  is  much  difference 
of  opinion  among  paint-making  mechanics  as  to  the 
proper  surface  which  a  grinding  surface  shall  present; 
for  instance,  the  first  depression  in  the  stone  of  a  mill 
is  deep,  tapering  toward  the  edge,  and  is  known  as  the 
"lead."  From  the  end  of  this  "lead"  fine  lines  radiate 
toward  the  "periphery"  of  the  stone.  These  are  called 
the  "drifts,"  and  the  paints  containing  silica  wear  off 
the  surface  of  even  the  hardest  flintstone  mills,  so  that 
in  well-regulated  factories  a  man  is  always  employed 
sharpening  the  mills,  and  by  the  term  "sharpening"  is 
understood  cutting  out  the  "drifts"  and  "leads." 

Not  so  many  years  ago  paint  mills  were  composed 
of  either  iron  or  steel,  but  in  modern  paint  practice  mills 
of  this  character  have  been  abandoned,  except  for  use 
as  filling  machines.  They  grind  fairly  fine  when  sharp, 


20  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

but  inasmuch  as  all  silicious  paint  materials  are  harder 
than  steel  or  iron  they  become  dull  in  a  very  short  time. 
Then  again,  the  attrition  grinds  off  small  particles  of 
iron,  which  affect  all  delicate  tints  more  or  less. 

The  arrangement  of  the  tanks  and  mills  in  the  factory 
is  of  the  greatest  importance.  Taking  up  first  the 
second  method  of  mixing  paint  already  described,  the 
liquid  and  white  base  are  mixed  in  large,  heavy  cast- 
iron  mixers,  which  are  located  on  a  platform  high 
enough  to  discharge  into  a  liquid  mill.  (See  Fig.  i, 
Heavy  Mixers.) 

The  mixed  material  is  ground  through  this  mill  and 
discharged  from  it  into  storage  tanks  situated  con- 
veniently on  a  platform  below  the  floor  on  which  the 
mill  is  located,  these  storage  tanks  holding  from  1500 
to  2000  gallons  of  the  ground  product.  From  the  stor- 
age tanks  a  pipe-line  with  its  various  branches  carries 
the  paint  to  tinting  tanks  placed  at  convenient  dis- 
tances from  the  storage  tanks,  the  latter  being  high 
enough  to  allow  the  paint,  by  gravity,  to  flow  through 
pipes  to  the  tinting  mixers.  This  pipe-line  is  made  of 
wrought  iron,  the  usual  diameter  of  which  is  4  inches, 
the  joints  being  all  flanged  so  that  the  pipes  may  be 
easily  taken  apart  and  cleaned. 

Underneath  the  storage  tanks  and  close  to  the  outlet 
is  a  master  valve,  so  that  the  product  in  the  tank  may  be 
shut  off  at  any  time  and  the  flow  cut  out  from  the  sys- 
tem of  pipes.  Opposite  each  tinting  tank  (these  tanks 
should  be  in  parallel  rows  and  numbered  to  correspond 
to  the  tints  that  are  to  be  made)  a  2-in.  branch  pipe  is 
connected  to  the  4-in.  main,  and  each  of  these  branches 
is  furnished  with  a  valve  to  control  the  discharge  into 
the  tinting  mixers.  The  cast-iron  mixers  already  men- 
tioned should  be  so  arranged  that  two  mixers  work  in 


THE  MANUFACTURE  OF  MIXED  PAINTS 


21 


conjunction  with  one  mill.  The  mill  is  of  stone  and 
known  as  a  liquid  or  incased  mill,  the  usual  diameter 
being  30  to  36  inches. 


jjj£-.      .  ORAGE  TANK  PLATFORM  Q 


FIG.  i — HEAVY  MIXERS 

The  storage  tanks  are  made  of  sheet  metal  with 
heavy  sheet-steel  bottoms,  and  are  furnished  with  a 
slowly  revolving  stirrer  to  keep  the  ground  liquid  agi- 
tated. The  outlet  of  these  tanks  is  of  generous  size  and 
covered  with. a  steel  wire  screen  to  prevent  any  foreign 


THE   MANUFACTURE    OF   MIXED    PAINTS  23 

matter  such  as  chips  of  wood  or  like  material  from  getting 
into  the  supply  pipes.  Fastened  to  the  stirrer  of  these 
tanks  is  a  wire  brush  which  scrapes  the  surface  of  the 
screen  in  its  rotation  around  the  tank,  thus  keeping  the 
holes  of  the  screen  free  for  the  proper  flow  of  the  liquid. 
The  tinting  colors  used  in  this  process  are  usually  ground 
through  small  stone  mills  of  15  in.  or  20  in.  diameter, 
and  are  stored  in  convenient  portable  receptacles. 

This  method  of  liquid  paint-making  reduces  the 
handling  and  labor  cost  to  a  minimum,  the  hardest  work 
being  done  on  the  mixer  platform  where  the  dry  pigment 
and  the  proper  amount  of  liquid  are  first  mixed.  In  a 
factor}7  where  the  floors  are  not  arranged  so  that  the 
method  already  described  can  be  carried  through  by 
gravity  alone,  it  is  possible  and  practicable  to  introduce 
a  force  pump,  preferably  of  the  rotary  type,  to  make  up 
for  this  deficiency.  When  this  latter  method  is  used, 
the  cast-iron  mixer  and  mill  should  remain  in  the  same 
relative  position  as  before,  but  the  storage  tank  could  be 
placed  in  any  other  part  of  a  building  and  on  the  same 
floor  as  the  liquid  mill,  but  high  enough  to  discharge 
by  gravity  into  the  tinting  mixers.  The  ground  pig- 
ment would  then  be  discharged  into  a  small  tank 
situated  at  the  foot  of  the  mill,  to  which  the  rotary  pump 
is  attached.  As  this  tank  is  filled  with  the  ground 
product,  the  pump  would  force  it  through  the  proper 
pipe  connection  to  the  storage  tank,  the  connection 
from  the  storage  tanks  to  the  tinting  mixers  being  the 
same  as  in  the  first  described  process. 

The  other  method  in  use  is  to  mix  and  grind  the 
pigment  in  paste  form,  using  the  same  style  of  mixer; 
but  instead  of  a  liquid  mill  a  paste  mill  is  used.  Situated 
at  the  back  of  this  paste  mill,  and  close  to  the  discharge 
scraper,  is  a  steel  tank  of  generous  dimensions  (usually 


24  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


THE  MANUFACTURE  OF  MIXED  PAINTS  25 

500  gallons),  into  which  the  ground  pigment  is  dis- 
charged. This  steel  tank  is  provided  with  a  stirrer  for 
mixing  the  ground  pigment  with  the  oil  and  other  thin- 
ners  that  are  added  to  it,  in  order  to  reduce  it  to  a 
liquid  form.  It  is  then  carried  to  the  tinting  tanks  by 
a  pipe-line  on  the  same  general  plan  as  that  heretofore 
described. 

One  of  the  advantages  of  this  plan  is  that  this  outfit 
can  be  used  in  a  dual  capacity,  i.e.  it  can  be  used  for 
the  mixing  of  liquid  paints  after  the  plan  described  and, 
by  changing  the  scraper  from  the  back  to  the  front  of 
the  mill,  the  outfit  can  be  changed  into  a  paste-grinding 
plant. 


THE    PIGMENTS 

CHAPTER  II 

THE  WHITE  PIGMENTS 

THE  white  opaque  pigments  used  in  making  mixed 
paints  are  white  lead,  zinc  oxid,  sublimed  white  lead, 
leaded  zincs,  lithopone,  and  other  zinc  and  lead 
pigments. 

Among  the  white  leads  there  are  several  varieties; 
the  principal  ones,  however,  are  the  old  Dutch  process 
lead  and  the  quick  process  lead,  both  of  which  are 
hydrated  carbonates  of  lead. 

There  are  many  varieties  of  zinc  oxid  made  in  the 
United  States,  depending  largely  upon  the  raw  material. 
The  grade  made  principally  from  spelter,  according  to  the 
French  process,  is  known  in  America  as  "Florence  Red" 
and  "Green  Seal  Zinc."  The  seals  on  zinc  indicate  the 
whiteness  of  color,  the  green  seal  being  the  whiter.  In 
Germany  the  colored  seals  extend  to  a  greater  range 
than  in  America,  the  green  seal  being  the  whitest,  the 
red  next,  the  blue  next,  the  yellow  next,  and  then  the 
white. 

The  New  Jersey  zinc  oxids  are  made  direct  from  the 
ore  and  are  almost  as  pure  as  the  zincs  made  from  the 
metal,  but  they  have  a  totally  different  tone,  being  much 
more  of  a  cream  color  than  the  so-called  French  zincs. 

The  Mineral  Point  zincs  made  in  Wisconsin  contain 
a  varying  percentage  of  sulphate  of  lead.  The  leaded 
zincs  of  Missouri  are  analogous  in  composition  to  those 

26 


WHITE  PIGMENTS  27 

of  Mineral  Point,  but  the  percentage  of  sulphate  of  lead 
is  much  higher. 

The  standard  zinc  lead  white  of  Colorado  contains 
50  per  cent  oxid  of  zinc  and  50  per  cent  sulphate  of 
lead.  Sublimed  white  lead  is  made  in  Joplin,  Missouri, 
from  Galena  mineral,  and  will  average  95  per  cent 
oxysulphate  of  lead  and  5  per  cent  zinc  oxid.  This 
material  has  been  largely  superseded  by  a  white  known 
as  Ozark  White,  which  is  described  under  that  heading. 

Lithopone  is  a  double  precipitate  of  sulphide  of  zinc 
and  sulphate  of  barium. 

These  are  the  opaque  white  pigments  used  in  the 
manufacture  of  mixed  paints.  It  is  not  within  the  power 
of  any  man  to  say  which  one  of  these  is  the  best,  because 
under  certain  circumstances  one  material  will  outrank 
another,  and  long  practice  has  demonstrated  that  no 
single  white  pigment  material  is  as  good  as  a  mixture  of 
various  white  pigments  for  mixed  paint.  The  differences 
of  opinion  and  conflicting  reports  that  one  hears  con- 
cerning these  raw  materials  are  largely  due  to  competi- 
tion among  manufacturers.  Whenever  a  new  material 
is  exploited  a  manufacturer  of  a  tried  and  staple  pig- 
ment naturally  finds  the  defects  in  the  new  material 
and  informs  his  salesmen  to  this  effect.  And  so  when  a 
material  finally  succeeds  and  takes  its  place  among  the 
recognized  list  of  pigments  it  has  gone  through  all  the 
hardships  and  vicissitudes  possible. 

For  two  thousand  years,  more  or  less,  there  was  no 
other  white  pigment  than  white  lead.  Within  the  life- 
time and  memory  of  many  a  paint  manufacturer  in  the 
United  States  all  the  pigments  described  in  the  beginning 
of  this  chapter  have  been  born  and  have  prospered. 
The  great  competitor  of  white  lead  is  zinc  oxid,  and  the 
weakness  of  white  lead  is  the  strength  of  zinc  oxid,  and 


28  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

vice  versa.  White  lead,  for  instance,  is.  a  soft  drier  and 
zinc  oxid  is  a  hard  drier.  White  lead  finally  becomes 
powdery;  zinc  oxid  in  its  eventual  drying  becomes  hard, 
and  it  is  for  these  reasons  that  a  mixture  of  zinc  oxid 
and  white  lead  forms  such  a  good  combination.  On  the 
other  hand,  it  is  regarded  as  a  fact  that  a  paint  com- 
posed of  an  opaque  white  pigment  in  a  pure  or  undiluted 
state  should  not  be  used,  for  experience  and  chemistry 
have  both  shown  that  an  inert  extender  added  in  mod- 
erate proportions  to  the  solid  white  pigment  increases 
its  wearing  power,  and  when  the  surface  finally  needs 
repainting  it  presents  a  better  foundation  for  future 
work.  Taking  all  of  these  facts  into  consideration,  a 
paint  manufacturer  who  combines  experience  with  the 
teaching  of  chemistry  is  quite  likely  to  produce  a  mate- 
rial that  will  add  both  to  his  reputation  and  his  income. 
He  certainly  has  a  great  advantage  over  the  man  who 
works  entirely  by  rule  "of  thumb. 

WHITE  LEAD 
Formula,  2PbC(VPb(OH)2;  Specific  Gravity,  6.323  to  6.492 

White  lead  is  the  oldest  of  all  white  paints,  and  prior 
to  the  middle  of  the  last  century  it  was  the  only  white 
pigment  in  use  with  the  exception  of  a  little  zinc  and  bis- 
muth. Within  half  a  century  quite  a  number  of  other 
white  pigments  have  come  into  use,  and  only  gradually 
have  the  defects  of  white  lead  become  known.  However, 
paint  manufacturers  in  the  United  States  are  very  large 
users  of  dry  white  lead,  which,  together  with  zinc, 
asbestine,  and  other  inert  materials,  forms  the  bases  or 
pigments  of  the  mixed  paints.  There  seems  to  be  an 
antagonism  against  the  use  of  white  lead  which  apparently 
is  unfounded,  for,  although  white  lead  may  have  its 


WHITE  PIGMENTS 


defects,  there  is  no  other  white  pigment  which  is  100 
per  cent  perfect,  and  therefore  it  is  only  fair  to  give  that 
time-honored  material  its  proper  due.  White  lead  as  a 
priming  coat  on  wood,  particularly  when  it  contains 
more  oil  than  should  normally  be  used,  cannot  be  ex- 
celled. 

The  history  of  this  pigment,  its  method  of  manu- 
facture, and  the  general  uses  to  which  it  has  been  applied 
are  so  well  known,  and  are 
generally  given  even  in 
elementary  text-books  on 
chemistry,  that  it  is  not 
the  author's  purpose  to 
take  up  much  space  for 
this  subject.  Briefly  stated, 
however,  there  are  two 
processes  for  the  manu- 
facture of  white  lead.  One 
is  called  the  Dutch  process, 

which    takes    about   ninety      No.  i.  CORRODED  WHITE  LEAD  —  Pho- 
dayS     and     is     a     slow     COr-          tomicrograph   X25°,  of  known  purity 
.  and  composition. 

rosion  of  a  buckle  of  lead 

in  an  earthenware  pot  in  the  presence  of  acetic  acid. 
Carbonic  acid  from  fermenting  tan  bark  acts  on  the 
lead,  converting  the  material  into  hydrated  carbonate 
of  lead.  In  the  other,  which  is  called  the  quick 
process,  the  acetic  acid  solution  is  directly  acted  upon 
by  either  carbonic  acid  gas  or  an  alkaline  carbonate 
salt.  The  old  Dutch  process  is  still  much  more  largely 
used  than  the  quick  process,  the  resulting  product  being 
much  more  desirable  from  the  practical  standpoint. 
There  are  a  number  of  other  processes  under  a  variety 
of  names,  but  none  of  them  differ  very  much  from  the 
so-called  "quick  process." 


30  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

White  lead  is  in  great  favor  with  the  practical  painter, 
not  for  its  wearing  quality,  but  principally  for  the  free- 
dom with  which  it  is  applied.  Although  white  lead  is 
generally  spoken  of  as  a  carbonate  of  lead,  it  is  com- 
posed of  approximately  69  per  cent  carbonate  of  lead, 
PbC03,  and  31  per  cent  of  lead  hydroxid,  Pb(OH)2. 
It  is  this  lead  hydroxid  which  combines  quite  rapidly 
with  oil  and  forms  an  unctuous  substance  sometimes 

known  as  "lead  soap." 
White  lead  is  variable  in 

^^  •-.  •••.?.>'.-, '-p-x         composition,    the    amount 

*  t  :  *     .       of  hydroxid   ranging  from 

4k  •  *•'      *"•*       **  '  T  *   "  "  '"•'"«•  MJ  :    t**  * 

"  •  *'  V;* ^v'i^'V&J?  : .,< ;•••*.  <>£»      15    to    30    per    cent.      In 

|    C--      '••      vW.-*»   '«,**   »*  *  "  *  'vt* '  -*&\T*'   '  v--Y"&  ' -*'        ""Cfc 

rr<".  •  ^^n^T^  m   addition    to    this,    during 

,:*  *.*  5^.?t<: '     ^H      ,  .... 

the  process  of  manufac- 
ture of  the  old  process 
lead,  and  after  its  final 
washing,  it  is  mixed  with 
linseed  oil  while  still  in 
the  wet  state.  The  oil 

No.    2.  OLD   PROCESS   WHITE    LEAD —      ,  „    . 

Photomicrograph  X25o.  having    a   greater   affinity 

for    the    white   lead    than 

the  water  has,  the  latter  is  displaced.  A  small  per- 
centage of  moisture  adds  to  the  free  working  quality  of 
the  paint  made  from  white  lead.  (See  "Water  in  the 
Composition  of  Mixed  Paints,"  page  255.) 

White  lead  is  regarded  as  a  poisonous  pigment,  and 
so  it  is,  but  this  property  should  not  condemn  it  for 
application  to  the  walls  of  a  house  or  for  general  paint 
purposes,  because  its  toxic  effect  cannot  be  produced 
from  a  painted  surface.  Its  poisonous  quality  is  mani- 
fest to  the  workmen  in  the  factories  where  white  lead  is 
made,  and  also  to  the  painter  who  is  careless  in  apply- 
ing it.  The  unbroken  skin  does  not  absorb  lead  very 


WHITE  PIGMENTS  31 

rapidly,  but  the  workman  inhaling  lead  dust,  or  the 
painter  who  allows  a  lead  paint  to  accumulate  under  his 
finger  nails,  is  likely  to  suffer  from  lead  poisoning.  In 
one  or  two  factories  where  much  white  lead  is  ground,  a 
small  percentage  of  potassium  iodide  is  placed  in  the 
drinking  water.  This  overcomes  •  any  tendency  toward 
lead  poisoning,  by  reason  of  the  fact  that  the  soluble 
iodide  of  lead  is  formed  in  the  system  and  the  lead  is 
thus  flushed  out  through 
the  kidneys.  Charles  Dick- 
ens, in  one  of  his  short 

stories    called    "A    Bright      4V^vV*  '-->  .< -*       <>       *4...*v 
Star   in    the   East,"    com-      ^^  txiJ&v  ^  :\$  ' 
ments  on  the  misery  pro-  jK**.*f%  • 
duced    in  a  certain  white  '         "" 

lead  factory  in  London, 
and  expressed  the  hope 
that  American  ingenuity 
would  overcome  the  dan- 
gers  which  beset  the  men. 
In  one  of  the  largest  white  No"  3"  ^™  LEAD  ("ew  Process)- 

rnotomicrograph  X25O. 

lead  works  in  New  York 

City  lead   poisoning   does   not   occur,    owing  to  the  in- 
genuity and   care  exercised  by   the  management. 

The  ratio  of  oil  necessary  to  reduce  white  lead  to  the 
consistency  of  paint  can  by  no  means  be  given  in  exact 
figures.  The  old  Dutch  process  lead  will  take  four  and  a 
half  gallons  of  linseed  oil  to  one  hundred  pounds  of  white 
lead  ground  in  oil,  in  order  to  obtain  a  paint  of  maxi- 
mum covering  property.  The  new  process  lead  will  take 
more  oil  than  this,  and  in  many  instances  up  to  six 
gallons  to  the  one  hundred  pounds  of  white  lead  paste, 
which  contains  approximately  iTV  gallons  of  linseed 
oil.  On  a  mixed  paint  basis,  60  pounds  of  dry  white 


32  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

lead  will  take  40  pounds  of  linseed  oil  to  produce  the 
correct  ratio,  but  in  addition  four  pounds  of  volatile 
thinner,  such  as  benzine  or  turpentine,  can  be  added  to 
increase  the  fluidity  and  assist  in  the  obliteration  of 
brush  marks.  No  general  rule  can  be  given  for  the  per- 
centage of  oil  necessary,  as  temperature  has  much  to  do 
with  this,  but  the  difference  in  the  amount  of  oil  neces- 
sary to  produce  a  good  flowing  paint  during  summer  or 
winter  can  be  approximately  given  as  10  per  cent,  less 
vehicle  being  necessary  in  summer  than  in  winter. 

White  lead  when  exposed  to  the  elements  becomes 
chalky  after  a  while  and  assumes  a  perfectly  flat  appear- 
ance which  resembles  whitewash,  and  comes  off  very 
readily  on  the  hand.  As  long  as  there  was  no  remedy 
for  this  there  was  no  comment  on  the  subject,  but  at  the 
present  time  investigators  have  improved  paint  mixtures 
so  that  this  defect  is  not  so  palpable  as  it  was  in  former 
years.  From  many  experiments  made  by  the  author 
the  causes  of  the  chalking  of  white  lead  may  be  sum- 
marized as  follows: 

First.     The  action  of  the  carbonic  acid  in  rain  water. 

Second.     The  action  of  sodium  chloride  (salt  in  the  air) . 

Third.  The  catalytic  action  of  white  lead  itself  in 
being  a  progressive  oxidizer  of  linseed  oil. 

First.  If  white  lead  be  treated  with  water  containing 
carbonic  acid,  it  is  found  that  the  same  solvent  action 
takes  place  upon  carbonate  of  lead  as  takes  place  upon 
calcium  carbonate. 

Second.  If  white  lead  be  treated  with  a  sodium  or 
ammonium  chloride  solution,  a  solvent  action  is  apparent, 
and  as  sodium  chloride  is  always  present  in  the  air  at  the 
seashore,  and  carbonic  acid  is  everywhere  present  in  the 
atmosphere  and  is  readily  taken  up  in  a  rain  storm,  the 
chalking  of  white  lead  can  be  attributed  to  these  causes. 


WHITE  PIGMENTS  33 

Third.  This  cause  is,  however,  problematical  and 
cannot  at  this  writing  be  stated  with  any  degree  of 
positiveness.  It  is  quite  true  that  white  lead  and  linseed 
oil  do  not  attack  each  other  so  readily  on  an  interior  wall 
as  they  do  on  a  wall  exposed  to  the  elements. 

One  of  the  defects  mentioned  by  many  writers  on 
white  lead  is  its  susceptibility  to  sulphur  gases.  In 
nature  these  sulphur  gases  are  generated  in  two  places; 
namely,  in  the  kitchen  of  every  house,  and  in  and  around 
stables  and  outhouses.  In  kitchens  the  cooking  of 
vegetables  liberates  hydrogen  sulphide  to  a  great  extent, 
the  odor  of  which  is  familiar  to  everybody  who  comes  into 
a  house  where  either  cauliflower  or  cabbage  is  being 
cooked.  But,  inasmuch  as  undiluted  white  lead  is  not 
often  used  for  interior  painting,  the  defect  is  not  so 
noticeable.  A  few  stables  or  outhouses  are  painted  pure 
white,  and  when  they  are  painted  white  the  painter 
generally  has  sufficient  knowledge  of  the  subject  to  use 
zinc  oxid  instead  of  white  lead. 

It  cannot  be  denied  that  the  ease  of  application  of 
white  lead,  as  well  as  its  enormous  covering  property, 
has  had  much  to  do  with  the  preference  for  it  as  a  paint. 
With  the  exception  of  lithopone,  it  has  a  greater  hiding 
property,  volumetrically  considered,  than  any  other  white 
paint;  on  the  other  hand,  gravimetrically  considered,  it 
has  less  body  than  any  of  the  lighter  paints. 

The  addition  of  an  inert  filler,  such  as  artificial  barium 
sulphate,  silica,  and  barytes,  improves  white  lead  con- 
siderably. These  inert  fillers,  which  will  be  considered 
under  their  proper  chapters,  are  not  affected  by  chemical 
influences  in  the  slightest  degree,  and  where  they  are 
used  in  the  proper  proportions  additional  wearing  quality, 
or  "life,"  as  the  painter  calls  it,  is  given  to  the  paint. 
The  percentage  of  inert  fillers  which  can  be  added  to 


34  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

white  lead  varies  up  to  50  per  cent.  More  artificial 
barium  sulphate  than  natural  barium  sulphate  can  be 
added.  If  a  comparative  exposure  test  be  made,  both 
on  wood  and  metal,  of  undiluted  white  lead  and  white 
lead  containing  an  inert  extender,  it  will  be  found  that 
at  the  end  of  eighteen  months  the  paint  which  contained 
the  filler  is  in  a  better  state  of  preservation  than  that 
which  did  not  contain  it.  Generally  considered,  white 
lead  is  an  excellent  paint,  more  particularly  when  added 
to  other  materials. 

SULPHATE  OF  LEAD 
Formula,  PbSCX;  Specific  Gravity,   6.2  to  6.38 

It  must  be  borne  in  mind  that  the  sulphate  of  lead 
of  commerce,  which  is  not  so  frequently  met  with  nowa- 
days as  formerly,  is  a  very  poor  paint  material,  and  it 
must  not  by  any  means  be  confounded  with  sublimed 
white  lead,  which  is  at  times  erroneously  called  lead 
sulphate. 

The  lead  sulphate  of  the  paint  trade  is  a  nondescript 
article  which  was  sold  as  a  by-product  by  the  textile 
printers  who  used  acetate  of  lead  as  a  mordant,  and  to 
this  liquid  sulphuric  acid  was  added  and  the  precipitate 
was  sold  to  the  paint  trade  under  the  name  of  lead 
bottoms  or  bottom  salts.  Occasionally  this  material  is 
still  met  with,  and  wherever  it  is  used  in  a  mixed  paint 
it  does  more  harm  than  good.  It  is  likely  that  the  pure 
neutral  lead  sulphate,  which  is  a  good  oxidizing  agent, 
dries  well,  and  covers  fairly  well,  could  be  used  for  ordi- 
nary light  tints  if  diluted  with  the  proper  inert  materials, 
but  the  lead  sulphate  which  is  sold  by  the  textile  printers 
is  always  acid  and  is  sometimes  coarse  and  crystalline, 
though  at  other  times  quite  fine.  The  chemist,  the  paint 


WHITE  PIGMENTS  35 

maker,  and  the  engineer  must  never  confound  this  lead 
sulphate  with  the  lead  sulphate  contained  in  sublimed 
lead,  zinc  lead,  or  leaded  zincs. 

SUBLIMED  WHITE  LEAD 
Specific  Gravity,  6.2 

Sublimed  white  lead  is  an  amorphous  white  pigment 
possessing  excellent  covering  and  hiding  power,  and  is 
very  uniform  and  fine  in  grain.  It  is  a  direct  furnace- 
product  obtained  by  the  sublimation  of  Galena,  and 
within  the  last  ten  years  it  has  come  into  great  prom- 
inence among  paint  makers,  now  being  regarded  as  a 
stable,  uniform,  and  very  valuable  paint  pigment.  The 
author  has  examined  a  great  many  paints  containing 
sublimed  lead.  Among  one  hundred  reputable  paint 
manufacturers  in  the  United  States  sixty-five  used  sub- 
limed lead.  About  eight  thousand  tons  wrere  used  in 
the  United  States  in  1905.  Considering  the  fact  that 
sublimed  lead  as  a  pigment  is  about  twenty-five  years 
old,  it  is  very  likely,  judging  from  its  qualities,  that  it 
will  be  used  more  universally  and  in  larger  quantities 
in  the  future. 

When  mixed  with  other  pigments,  such  as  zinc  oxid, 
carbonate  of  lead,  and  the  proper  reducing  materials 
added,  such  as  silica,  clay,  barium  sulphate,  etc.,  it  pro- 
duces a  most  excellent  paint,  and  at  the  seashore  its 
wearing  quality  is  superior  to  that  of  carbonate  of  lead. 
In  composition  it  is  fairly  uniform.  From  the  analyses 
of  thirty-four  samples  of  sublimed  lead  its  composition 
may  be  quoted  as  75  per  cent  lead  sulphate,  20  per  cent 
lead  oxid,  and  5  per  cent  zinc  oxid,  although  each  of 
these  figures  will  vary  slightly  either  way.  Corroded 
white  lead  also  varies  in  its  percentage  of  hydroxid,  but 


CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 


for  analytical  purposes  a  constant  must  be  admitted 
which  will  fairly  represent  the  composition. 

The  question  has  arisen  of  late  years  whether  sublimed 
lead  is  a  mixture  of  the  three  components  just  cited,  or 
whether  it  is  a  combination  of  lead  sulphate  and  lead 
oxid  with  the  mechanical  addition  of  zinc  oxid*  Inas- 
much as  all  the  lead  oxids  that  are  known  in  commerce 
or  in  chemistry  are  yellow,  red,  or  brown  it  is  held  by 

many  that   the   lead  oxid 

of  sublimed  lead  is  really 
an  oxysulphate,  or,  in 
other  words,  a  basic  sul- 
phate of  lead.  A  mixture 
of  precipitated  lead  sul- 
phate, litharge,  and  zinc 
white  in  approximately  the 
proportions  found  in  sub- 
limed lead,  when  ground 
in  oil  and  reduced  to  the 
proper  consistency,  dries 

No.  4.   SUBLIMED  WHITE  LEAD-Pho-      totall      different    from   sub_ 
tomicrograph  X25O,  showing  great  urn- 

formity  of  grain.  limed  white  lead;  in  fact, 

sublimed  lead  when  ground 

in  raw  linseed  oil  takes  two  days  to  dry  dust  free,  but  the 
mixture  just  cited  will  dry  sufficiently  hard  for  repaint- 
ing in  twelve  hours,  because  lead  sulphate  is  a  fair  drier 
and  lead  oxid  a  powerful  one.  Yet  the  oxysulphate,  hav- 
ing the  same  composition,  behaves  totally  differently  from 
the  mixture  and  in  addition  is  of  a  different  color. 

Under  the  microscope  sublimed  lead  shows  the 
absence  of  crystals  and  remarkable  uniformity  of  grain. 
Being  a  much  more  inert  chemical  body  than  the  other 
lead  paints,  it  does  not  react  on  linseed  oil,  and  there- 
fore makes  a  much  more  durable  paint  compound.  It 


1 


WHITE  PIGMENTS  37 

has  been  urged  that  sublimed  lead  is  not  as  susceptible 
to  sulphur  gases  as  white  lead,  but  this  the  author 
has  not  been  able  to  substantiate,  for  while  it  may  take 
hydrogen  sulphide  a  longer  time  to  discolor  it,  it  is 
simply  a  question  of  degree  and  it  is  acted  upon  by  sul- 
phur gases,  although  not  as  quickly  as  white  lead. 

Sublimed  lead  can  be  determined  in  a  white  mixed 
paint  without  any  difficulty,  owing  to  the  established 
ratio  between  lead  oxid  and  lead  sulphate.  The  per- 
centage of  free  zinc  sulphate  in  sublimed  white  lead 
varies  from  a  trace  to  a  half  per  cent,  and  many  times  a 
chemist  will  report  more  zinc  sulphate  than  is  actually 
present,  because  in  washing  or  boiling  a  dry  or  extracted 
sample  the  lead  sulphate  may  interact  with  the  zinc 
oxid  and  show  a  larger  percentage  of  zinc  sulphate  than 
is  really  present  in  the  dry  products  before  analysis. 

Sublimed  white  lead  as  a  marine  or  ship  paint  is  of 
much  value,  owing  to  its  hardness  of  drying  and  imper- 
viousness  of  film. 

'    STANDARD  ZINC  LEAD  WHITE 

The  ores  utilized  in  the  manufacture,  of  this  material 
are  what  are  known  in  mining  parlance  as  "Low  Grade 
Complex  Ore,"  originating  in  and  about  Leadville,  Colo- 
rado; Low  Grade,  inasmuch  as  the  gold,  silver,  and  cop- 
per are  present  in  quantities  too  small  to  warrant  the 
excessive  cost  of  refining.  Naturally  this  ore  contains 
varying  percentages  of  zinc  blende  or  sphalerite  and 
Galena  or  native  lead  sulphide,  and  in  order  to  furnish 
the  product  with  the  proper  proportions  of  lead  and  zinc 
the  ores  are  first  analyzed,  then  mixed  in  their  proper 
proportions,  and  volatilized  at  a  heat  of  from  2200  to 
2500°  F.  In  the  volatile  state  it  is  carried  to  the  com- 
bustion chamber,  where  the  chemical  transformation  of 


38  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

the  product,  due  to  oxidation,  completes  itself.  The 
white  fume  is  collected  in  woolen  bags,  further  oxidized 
on  open-hearth  furnaces,  whitened,  and  then  bolted. 

The  pigment  carries  approximately  50  per  cent  pure 
zinc  oxid  and  50  per  cent  lead  sulphate,  which  have 
combined  at  an  intense  heat  in  vapor  form,  the  union 
being  far  more  intimate  than  anything  that  could  be 
obtained  by  mechanical  means. 

This  pigment  was  first 
put     upon      the      market 
twenty-four  years  ago,  and 
had   been   popular   in  the 
mixed  paint   trade    for    a 
receding    ten 
the  last 
it  had 
uniform  and 

j?          able  paint  material  by  a 
i**v*-L*  great    many   mixed    paint 

No.  5.   STANDARD  ZINC  LEAD  WHITE —  - 

Photomicrograph  X25°.  manufacturers.     However, 

this  material  is  at  pres- 
ent not  manufactured,  but  has  been  largely  superseded 
by  a  white  known  as  Ozark  White,  which  will  be  de- 
scribed under  that  heading. 

The  color,  while  it  is  not  as  white  as  zinc  oxid,  is 
about  the  same  shade  as  the  average  corroded  white 
lead.  The  pigment  can  be  used  to  great  advantage 
in  combination  leads,  graded  leads,  primers,  floor  paints, 
and  ready  mixed  paints.  Its  specific  gravity  is  approxi- 
mately 5.5,  and  its  composition  theoretically  50  per 
cent  pure  zinc  oxid  and  50  per  cent  lead  sulphate. 
The  pigment  generally  contains  a  trace  of  silica,  iron,  and 
alumina.  A  very  small  portion  of  the  lead  is  in  the 


WHITE  PIGMENTS  39 

form  of  a  basic  lead  sulphate,  and  the  pigment  un- 
doubtedly takes  up  a  little  moisture  on  standing.  Its 
average  analysis  shows  the  following  composition: 

PbSO4 50.00  per  cent 

ZnO 49-55  Per  cent 

ZnSO4 0.40  per  cent 

The  percentage  of  zinc  sulphate  will  vary  slightly, 
but  under  normal  conditions  it  will  seldom  average  higher 
than  \  of  i  per  cent,  and  where  it  does  average  more  than 
this  it  is  frequently  due  to  long-continued  boiling  in  the 
flask,  which  causes  a  reaction  between  lead  sulphate  and 
zinc  oxid. 

ANALYSES  OF  STANDARD  ZINC  LEAD  WHITE 

PbSO4 48.90    50.00    49.22    49.80    50.15    48.87 

ZnO 50.50    49.55     50.41     49.90    49.25     50.82 

ZnSC>4 0.25       0.40    Trace      0.20      0.12    Trace 

Photomicrographs  of  zinc  lead  show  a  uniformity  of 
grain,  and  microscopic  investigations  fail  to  show  anything 
but  a  homogeneous  product.  It  is  very  stable.  When 
exposed  to  the  air  in  a  thin  film,  mixed  with  a  proper 
proportion  of  linseed  oil  and  drier,  it  retains  its  gloss 
longer  and  chalks  less  than  a  similar  film  containing  a 
mixture  of  50  per  cent  corroded  white  lead  and  50  per 
cent  zinc  oxid.  Like  white  lead,  it  whitens  on  exposure, 
but  holds  up  in  suspension  better,  as  indicated  by  its 
low  specific  gravity.  When  a  paint  is  made  on  a  zinc 
lead  base  ground  in  pure  linseed  oil  it  will  not  separate, 
form  a  cake,  or  yield  a  sediment;  neither  will  it  peel, 
chalk  off,  or  turn  yellow. 

OZARK  WHITE 

Ozark  White  is  a  very  desirable  pigment  and  has  all 
of  the  good  qualities  of  Standard  Zinc  Lead  White  and 


40  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Sublimed  White  Lead.  It  is  very  largely  used  in  the 
manufacture  of  mixed  paint.  In  many  respects  it  is 
superior  to  the  old  Standard  Zinc  Lead  White,  because 
its  approximate  composition  is  60  per  cent  of  zinc  oxid 
and  40  per  cent  of  lead  sulphate. 

The  process  is  so  highly  perfected  that  the  manu- 
facturers can  control  the  composition  so  as  to  insure  a 
variation  of  not  over  2  per  cent,  and  with  rare  exceptions 

the  material  does  not 
vary  i  per  cent  from  the 
composition  given.  To 
attain  this  degree  of  uni- 
formity, a  complete  anal- 
ysis of  every  car  of  ore 
is  made  as  soon  as  it  is 
received  before  passing  it 
to  the  mechanical  mixers. 
At  the  mixers  another 
analysis  is  made,  and  an 
ore  higher  in  zinc  or  lead 

No.  6.   OZARK  WHITE— Photomicrograph  111 

X300.  added,   as    the    case    may 

require,   in  order   to   have 

the  proper  metal  constituents.  The  ore,  after  being 
mixed  with  the  proper  proportion  of  coal  and  antiflux- 
ing  material  (crushed  silicious  rock  or  mine  screen- 
ings), is  charged  into  furnaces  which  have  previously 
been  bedded  with  a  sufficient  amount  of  coal  to  start 
combustion.  The  furnaces  are  then  sealed,  allowing  the 
temperature  to  rise  to  about  2300°  F.,  at  which  point 
it  is  held  until  the  zinc  and  lead  pass  off  together  in  the 
form  of  fume,  which  is  conducted  by  means  of  suction 
fans  through  pipe-lines  for  a  distance  of  about  500  feet, 
where  it  enters  large  brick  bag  houses.  The  fumes 
have  by  this  time  lost  considerable  of  the  heat,  so  that 


WHITE  PIGMENTS  41 

they  may  be  gathered  into  fabric  bags,  where  the  gases 
pass  out  and  the  pigment  is  collected.  From  the  bag 
house  the  pigment  is  conveyed  to  an  automatic  packer 
and  placed  in  barrels  of  suitable  weight,  and  is  then 
ready  for  the  consumer. 

An  actual  chemical  analysis  of  an  average  type  cf 
Ozark  White  shows  the  following: 

ZnO 59-32  per  cent 

PbS04 39-05  "  " 

ZnSO4 0.78  "      " 

SO2 0.05  "  " 

H20 0.66  "  " 

AsaOg 0.12  "      " 

Total  99.98  per  cent 

ZINC  OXID 
Formula,  ZnO;  Specific  Gravity,  5.2 

Zinc  oxid  as  a  paint  pigment  is  only  sixty  years  old, 
and  when  it  is  taken  into  consideration  that  in  that  short 
space  of  time  its  use  has  grown  until  in  1905  nearly 
seventy  thousand  tons  were  used  in  the  paint  industry 
in  the  United  States,  it  speaks  for  itself  that  the  material 
must  be  of  exceptional  merit  to  have  advanced  so  rapidly. 
At  the  same  time,  although  it  is  impossible  to  obtain 
any  exact  figures  on  the  subject,  it  is  probable  that 
more  than  one  half  of  these  seventy  thousand  tons  was 
used  in  connection  with  other  materials. 

The  discovery  of  zinc  oxid  by  Le  Clair  in  France  and 
Samuel  T.  Jones  in  America  is  sufficiently  well  known, 
and  has  been  quite  thoroughly  written  up  in  other  books. 
The  former  made  zinc  oxid  by  subliming  the  metal;  the 
latter  made  it  by  subliming  Zincite  and  Franklinite  ores. 
The  specific  gravity  of  zinc  oxid  will  average  5.2,  and 
fifty  pounds  will  take  fifty  pounds  of  linseed  oil;  in  other 


42  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

words,  to  produce  the  proper  mixed  paint  it  will  require 
a  far  greater  proportion  of  linseed  oil  than  white  lead  will 
take.  It  is  generally  stated  in  text-books  that  zinc 
oxid  is  not  affected  by  sulphur  gases  and  therefore 
will  not  turn  color.  This  statement  is  not  exactly 
correct;  the  author  always  contended  that  zinc  oxid  is 
not  visibly  affected  by  sulphur  gases,  but  there  is  no 
doubt,  as  any  chemist  will  admit,  that  zinc  oxid  is 
affected  by  sulphur  gases,  although  not  to  the  same 
extent  as  white  lead.  As  zinc  sulphide,  zinc  sulphite, 
and  zinc  sulphate  are  white  products,  the  absorption  is 
not  evident  to  the  eye,  and  hence  the  erroneous  state- 
ment has  crept  into  use  that  zinc  oxid  is  not  affected 
by  sulphur  gases. 

When  mixed  with  linseed  oil  and  the  proper  amount 
of  drier,  it  sets  and  dries  much  more  slowly  than  white 
lead.  Nevertheless  this  drying  continues  in  the  form  of 
progressive  oxidation  until  the  surface  becomes  very  hard. 
A  comparison  between  zinc-oxid  and  white-lead  paints 
will  show  that  the  progressive  oxidation  which  takes 
place  when  white  lead  dries  produces  a  chalky  mixture, 
while  the  reverse  is  true  of  zinc  oxid,  which  will  produce 
a  hard  and  brittle  vitreous  surface  which  is  somewhat 
affected  by  temperature  changes.  Owing,  therefore,  to 
the  diverse  effects  of  the  two  pigments,  a  combination 
of  lead  and  zinc  is  often  well  recommended.  The  hard 
drying  zinc  has  not,  however,  been  very  well  understood. 
Fifteen  years  ago  the  author  undertook  a  series  of  experi- 
ments and  found  that  the  drier  was  very  largely  respon- 
sible for  the  hardening  action  of  zinc.  If  the  linseed 
oil  be  prepared  with  litharge  (PbO),  the  resulting  zinc 
paint  will  last  far  longer  and  be  much  more  flexible  and 
consequently  not  readily  cracked  when  exposed  to  a 
variation  of  temperature  of  even  130°  F.,  such  as  we  have 


WHITE  PIGMENTS 


43 


in  this  climate.  If,  however,  a  drier  is  used  in  which 
manganese  (Mn02)  and  red  lead  (Pb3O4)  have  been  cooked 
with  the  oil,  the  action  of  the  manganese  continues  until 
a  vitreous  surface  is  the  result.  It  is  owing  to  the  result 
of  these  investigations  that  the  use  of  American  zinc 
oxid  made  from  Franklinite  ore  has  become  so  general 
for  the  manufacture  of  white  table  oilcloths.  (See 
Journal  of  Society  of  Chemical  Industry,  No.  2,  Vol. 
XXI,  Jan.  31,  1902.) 

When  enamel  paints 
are  made  of  an  oil  var- 
nish and  zinc  oxid,  and 
the  drier  in  the  varnish 
is  composed  of  manga- 
nese and  lead,  the  enamels 
^ 

eventually  become  hard, 
evidently  through  the  cata- 
lytic action  of  the  man- 
ganese. It  is  desirable  to 
omit  the  manganese  in 
high  grade  enamels,  or, 
where  manganese  must  be 
used  in  order  to  obtain 
a  rapid  setting,  the  borate  of  manganese  should  be 
employed,  but  only  in  very  small  quantities. 

The  American  zincs  are: 

First.  The  Florence  Red  and  Green  Seal  zincs,  which 
are  made  by  the  sublimation  of  the  metal  and  are  prac- 
tically pure  and  equal  in  all  respects  to  those  made  in 
France  and  Belgium. 

Second.  The  New  Jersey  zinc  oxids,  which  are  made 
from  Franklinite  ore  and  are  free  from  lead  and  fre- 
quently run  over  99  per  cent  ZnO. 

Third.     Mineral  Point  zinc,  which  is  made  at  Mineral 


No.  7.  AMERICAN  ZINC  Oxro  —  Photo- 
micrograph X3oo,  very  pure  and  very 
uniform  in  grain;  this  oxid  is  made 
direct  from  the  ore. 


44 


CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 


Point,  Wisconsin,  and  contains  from  2  to  4  per  cent  of 
lead  sulphate. 

Fourth.     The   leaded  zincs   made  in   Missouri,  which 
contain  from  4  to  10  per  cent  of  sulphate  of  lead. 

Zinc  oxid  chalks  to  some  extent  in  the  same  manner 
as  white  lead,  but  only  if  the  atmosphere  is  charged  with 
carbon  dioxid  or  salt.  The  same  experiment  which  was 
^^^^  carried  out  with  white 

^^  lead  in  order  to  show  its 

solubility  in  a  solution  of 
carbon  dioxid  was  carried 
zinc    oxid    and 
result  obtained, 
ight    cannot    be 
these     experi- 
because  these  chemi- 
always  present 
in  the  atmosphere.     They 
No.  8.  FRENCH  GREEN  SEAL  OXID-     are  merely  chemical  results 

Photomicrograph   X3oo,  much  whiter      which      demonstrate      both 
than  the  American  zinc  made  from  the      fL_    oonc<*    onrl     #>flWf      Knf 

,  .  L11C     CdU.SC      ctllU.      C11CL-L.      UU.L 

metal,  but  coarser  in  gram. 

it   is    of  some   interest   to 

know  why  the  paint  films  perish.  The  zinc  oxids  made 
from  western  ores  are  slightly  more  permanent  than 
those  made  from  the  New  Jersey  ores,  and  as  paint 
materials  they  possess  the  advantage  of  containing  a 
larger  quantity  of  lead  sulphate. 

Nearly  all  zincs  contain  a  small  percentage  of  zinc 
sulphate.  Much  unnecessary  trouble  has  been  caused 
by  the  criticism  against  zinc  sulphate.  Where  a  paint 
contains  moisture  or  where  water  is  added  in  a  very 
small  amount  to  a  heavy  paint  in  order  to  prevent  it 
from  settling,  and  not  more  than  one  per  cent  of  actual 
water  is  contained  in  the  paint,  zinc  sulphate  forms  an 


WHITE  PIGMENTS  45 

excellent  drier,  particularly  where  it  is  desirable  to  make 
shades  which  contain  lampblack.  The  outcry  against 
zinc  sulphate  is  unwarranted,  because  as  much  as  5  per 
cent  is  used  in  making  a  patent  drier.  The  amount  of 
zinc  sulphate,  however,  in  most  of  the  dry  zinc  pigments 
probably  decreases  with  age.  Zinc  oxid  or  other  zinc 
paint  which  will  assay  i  per  cent  of  zinc  sulphate  will, 
when  kept  in  storage  for  six  months,  show  a  decrease  in 
the  zinc  sulphate  to  one  half  of  i  per  cent. 

In  the  enamel  paints  the  presence  of  zinc  sulphate  is 
not  a  detriment,  and  in  floor  paints  it  might  be  con- 
sidered as  a  slight  advantage,  for  it  aids  in  the  drying 
and  hardening.  However,  too  much  of  the  soluble  salt 
is  never  to  be  recommended. 

ZINOX 

This  is  a  hydrated  oxid  of  zinc  not  manufactured  in 
this  country,  but  made  and  used  almost  entirely  in 
France.  It  is  not  yet  sold  dry,  but  generally  sold  either 
in  the  form  of  a  ready  mixed  enamel  or  in  a  semi-paste 
form,  and  is  presumed  to  possess  advantages  over  zinc 
oxid.  From  experiments  which  the  author  made  it  has 
been  found  that  the  hiding  power  and  working  quality 
are  practically  the  same  as  that  of  zinc  oxid.  It  pos- 
sesses, therefore,  no  marked  advantage  over  a  zinc  oxid 
enamel,  although  it  is  stated  that  it  remains  in  sus- 
pension longer  than  any  other  pigment.  The  zinc  oxid 
enamels  all  remain  in  suspension  a  very  long  time,  and 
even  though  they  settle  they  do  not  settle  very  hard  and 
can  be  very  easily  stirred.  In  thinner  media,  such  as 
are  used  for  the  manufacture  of  flat  wall  paints,  the 
hydroxid  of  zinc  has  some  advantage  over  the  oxid,  as  it 
produces  a  paint  that  remains  in  suspension  longer  and 
is  more  ready  for  use  than  that  made  from  the  oxid. 


46  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

LlTHOPONE 

Synonym  :  Oleum  White,  Beckton  White,  Charlton  White,  Pono- 
lith,  Jersey  Lily  White,  Orr's  White 

Chemical  Formula,  ZnS  +  BaS04;  Specific  Gravity,  4.2 

When  solutions  of  zinc  sulphate  and  barium  sulphide 
are  mixed  together  in  molecular  proportions  a  heavy 
flocculent  precipitate  is  formed  according  to  the  following 
reaction :  ZnSO4  +  Aq  +  BaS  +  Aq  =  ZnS  +  BaS04  +  H2O. 
The  theoretical  percentage  will  be  about  29!  per  cent 
zinc  sulphide  and  70 J  per  cent  barium  sulphate.  This 
precipitate  as  such  has  no  body  or  covering  power,  and 
when  washed  and  dried  is  totally  unfit  for  paint  pur- 
poses; but  John  B.  Orr,  of  England,  in  1880  discovered 
that  when  it  is  heated  to  dull  redness,  suddenly  plunged 
into  water,  ground  in  its  pulp  state,  thoroughly  washed 
and  dried,  its  characteristics  are  totally  changed,  and  it 
makes  a  very  effective  and  durable  pigment  for  paint 
purposes.  In  the  first  place,  it  is  then  a  brilliant  white; 
in  the  second  place,  it  is  extremely  fine  in  texture;  and 
in  the  third  place,  it  has  more  hiding  power  than  pure 
zinc  oxid.  Owing  to  its  chemical  composition  it  is 
stable  in  every  medium  known  for  paint  purposes,  except- 
ing those  which  are  highly  acid.  It  took  several  years 
to  perfect  the  manufacture  of  lithopone,  but  it  may  be 
easily  said  that  at  the  present  time  lithopone  is  made 
with  great  uniformity  and  has  valuable  properties,  as 
will  hereinafter  be  shown. 

The  method  of  manufacture  is  quite  simple,  success 
depending  very  largely  on  the  purity  of  certain  materials. 
It  is  worthy  of  mention,  however,  that  the  average  chem- 
ist unfamiliar  with  both  the  theory  and  practice  of  its 
manufacture  cannot  make  it  successfully.  In  the  first 
place,  solutions  of  barium  sulphide  and  zinc  sulphate  of 


WHITE  PIGMENTS 


47 


known  composition  must  be  made.  The  fact  that  they 
are  impure  has  no  effect  on  the  ultimate  product,  provided 
the  chemist  knows  the  impurities  he  has  to  deal  with 
and  the  simple  methods  for  their  elimination.  For 
instance,  the  zinc  sulphate  must  be  free  from  iron  or  a 
yellowish  product  is  the  result.  The  solutions  must  be 
standardized  for  each  batch.  The  impurities  can  be 
eliminated  during  the  process  of  manufacture,  or,  more 
properly  speaking,  before  they  are  pumped  into  the  pre- 
cipitation tub. 

The  barium  sulphide,  however,  is  quite  pure,  for  the 
reason  that  metals  like  copper,  iron,  and  manganese 
which  are  likely  to  be 
present,  form  insoluble  sul- 
phides. Barium  sulphide  is 
made  by  heating  barytes 
(BaSO4)  to  dull  redness 
with  coal,  petroleum  re- 
siduum, pitch,  sawdust,  or 
other  materials  having  a 
high  percentage  of  carbon. 
The  resulting  reaction  may 
be  represented  by  the 
following  equation:  BaS04 
+  4C  =  BaS  +  4CO,  al- 
though under  many  cir- 
cumstances the  reaction  is  more  slightly  complicated. 
After  the  reaction  is  completed  and  before  the  air  can 
have  any  influence  on  the  sulphide,  the  mass  is  digested 
in  vats  and  filtered;  when  the  solution  reaches  a  density 
of  17°,  Baume  long,  yellowish,  needle-shaped  crystals 
separate  from  the  mother  liquor.  These  crystals  are 
almost  chemically  pure  barium  sulphide. 

With  the  proper  concentration  of  the  solutions,  proper 


No.  9.  LITHOPONE  (dry)  —  Photomi- 
crograph X250,  exceedingly  fine  and 
uniform  in  grain. 


48  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

temperature  and  speed  at  which  the  two  solutions  are 
poured  together,  the  resulting  precipitate  will  be  of  such 
physical  characteristics  that  it  can  be  most  easily  filtered 
and  dried.  It  is  then  placed  in  muffles  and  heated  above 
920°  Fahrenheit,  suddenly  plunged  into  water,  again 
ground,  washed,  and  dried.  It  is  then  ready  for  the  mar- 
ket. The  overheating  of  the  precipitate  decomposes  some 
of  the  zinc  sulphide  and  converts  it  into  zinc  oxid.  All 
of  the  earlier  manufacturers  overheated  their  product,  and 

that  is  the  reason  why  litho- 
pone  formerly  contained 
from  5  to  10  per  cent  zinc 
oxid,  whereas  theoretically 
it  should  have  contained 
none.  The  manufacturers 
of  the  present  day,  however, 
have  overcome  all  these  dif- 
ficulties, so  that  a  remark- 
ably uniform  product  is 
obtained,  the  percentage  of 
No.  10.  LITHOPONE  (ground  in  oil)  —  zinc  oxid  being  small  indeed. 
Photomicrograph  xaso,  exceedingly  ^/"e  have  here  an  excel- 


lent example,  as  has  been 

stated  under  another  chapter,  of  a  pigment  containing  70 
per  cent  barium  sulphate,  which  may  be  regarded  as 
perfectly  pure  and  normal,  and  yet  twenty-five  years 
ago  any  pigment  containing  far  less  barium  sulphate 
than  lithopone  would  have  been  regarded  as  adulterated. 
No  man  can  reasonably  state  that  barium  sulphate  is  an 
adulterant  to  lithopone,  for  the  obvious  reason  that  it  is 
a  constituent  part  of  the  pigment. 

Lithopone  has  gone  through  many  vicissitudes;  no 
pigment  has  been  blackguarded  quite  as  much  as  this, 
and  yet  no  pigment  has  survived  its  condemnation  as 


WHITE  PIGMENTS  49 

well  as  this.  Almost  every  paint  manufacturer  in  the 
United  States  finds  some  excellent  use  for  it.  Within 
the  last  seven  or  eight  years  lithopone  has  come  into  its 
own,  and  today  there  is  no  paint  manufacturer  in  the 
United  States,  to  the  best  of  the  author's  knowledge, 
who  does  not  use  this  material.  Ten  years  ago  very 
few  paint  manufacturers  used  it  at  all. 

Since  1906  many  chemists,  including  such  capable 
men  as  Professor  Ostwald,  have  attempted  to  find  the 
cause  of  the  darkening  of  lithopone  in  sunlight.  When 
night  comes  a  change  takes  place,  and  the  following 
morning  lithopone  is  as  white  as  it  ever  was.  This 
property  is  called  the  "photogenic"  quality.  This  photo- 
genic action  goes  on  continually,  and  there  have  been 
a  large  number  of  investigators  who  have  attempted  to 
overcome  this,  and  a  review  of  the  literature  shows  that 
most  of  the  methods,  with  two  or  three  exceptions,  have 
been  empirical.  It  has  remained,  however,  for  Professor 
W.  D.  Bancroft  of  Cornell  University  to  delegate  one 
of  his  students,  W.  J.  O'Brien,  to  make  these  investiga- 
tions, and  the  full  account  is  recorded  in  Volume  XIX 
of  the  Journal  of  Physical  Chemistry,  113-44  (1915); 
an  extract  is  herewith  given  of  the  phenomenon. 

That  the  darkening  in  sunlight  is  due  to  the  formation 
of  zinc  from  zinc  sulphide  was  shown  by  the  fact  that 
the  dark  product  reduced  ferric  alum,  as  shown  by  the 
appearance  of  a  blue  color  with  potassium  ferricyanide, 
and  that  it  is  readily  soluble  in  acetic  acid,  in  alka- 
lies, and  in  solutions  of  sodium  chloride  and  sodium  sul- 
phate. The  zinc  is  a  direct  product  of  the  action  of  light  on 
zinc  sulphide.  The  results  of  the  investigation  are  sum- 
marized as  follows:  Quenching  in  water  prevents  further 
oxidation  of  the  red-hot  zinc  sulphide.  It  also  disinte- 
grates the  semi-fused  mass  and  dissolves  out  most  of  the 


50  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

soluble  salts.  Heating  the  barium  sulphate-zinc  sulphide 
precipitate  is  necessary  to  dehydrate  the  zinc  sulphide 
and  to  change  its  physical  condition,  so  that  it  forms  a 
dense  mass  with  good  body  which  can  be  ground  more 
readily.  The  yellow  color  produced  on  overheating  is 
due  to  an  oxid  film,  as  was  shown  by  Farnau.  The 
darkening  of  lithopone  is  not  due  to  impurities  such  as 
iron,  lead,  cadmium,  etc.  The  presence  of  salts  which 
form  soluble  zinc  salts,  such  as  sodium  chloride,  sodium 
sulphate,  etc.,  accelerates  the  darkening  of  the  lithopone. 
These  salts  dissolve  away  the  zinc  oxid  film.  This  is  simi- 
lar to  the  behavior  of  magnesium  in  water.  Magnesium 
does  not  decompose  water  very  readily  at  ordinary 
temperatures.  In  the  presence  of  magnesium  chloride, 
however,  the  action  takes  place  vigorously.  The  pres- 
ence of  salts  which  form  insoluble  zinc  salts,  such  as  the 
alkaline  phosphates,  bicarbonates,  ferrocyanides,  and  bo- 
rates,  retards  or  prevents  the  darkening  of  lithopone.  The 
action  of  light  on  the  zinc  sulphide  is  a  reducing  one, 
hydrogen  sulphide  and  metallic  zinc  being  formed.  The 
reaction  is  not  a  reversible  one;  the  metallic  zinc  formed 
is  oxidized  to  zinc  oxid;  barium  sulphate  is  not  neces- 
sary for  the  darkening  of  the  zinc  sulphide.  Heating  the 
zinc  sulphide  is  not  necessary  to  get  it  to  darken,  al- 
though heating  makes  the  zinc  sulphide  more  sensitive 
to  light,  probably  because  the  reducing  atmosphere  and 
the  sodium  chloride  used  remove  the  zinc  film  more 
readily.  The  zinc  oxid  film  can  be  removed  by  boiling 
in  a  concentrated  solution  of  zinc  chloride.  The  zinc 
sulphide  so  treated  will  darken  in  the  presence  of  a 
reducing  agent.  When  barium  sulphate  is  precipitated 
with  the  zinc  sulphide,  it  aids  the  darkening,  due  to  the 
fact  that  it  adsorbs  the  zinc  sulphide,  thereby  giving 
increased  surface  exposure  of  the  zinc  sulphide.  It 


WHITE  PIGMENTS  51 

probably  also  adsorbs  the  metallic  zinc.  The  zinc  sul- 
phide will  darken  without  the  presence  of  a  reducing 
agent  if  it  is  precipitated  with  barium  sulphide  and 
boiled  in  a  concentrated  solution  of  zinc  chloride.  The 
barium  sulphate  probably  adsorbs  metallic  zinc  as  well 
as  zinc  sulphide,  thus  making  the  latter  sensitive  to 
light.  The  patented  processes  for  the  prevention  of  the 
darkening  of  lithopone  depend  upon  the  formation  of  an 
insoluble  film  around  the  zinc  sulphide.  It  is  impossible 
to  make  a  lithopone  that  will  not  darken  unless  there  is  a 
film  protection  of  some  kind  over  the  zinc  sulphide.  A 
lithopone  of  good  quality  that  would  not  darken  was 
made  by  producing  an  oxid  film  on  the  zinc  sulphide  and 
keeping  the  oxid  content  above  3  per  cent  and  below  5 
per  cent.  Aluminium  oxid  can  be  substituted  for  the 
zinc  oxid.  A  film  of  sulphur  protects  to  some  extent; 
no  experiments  were  made  to  determine  the  maximum 
efficiency  possible. 

From  the  above  we  can  readily  see  that  the  theory  is 
a  tenable  one,  and  that  the  action  of  light  on  zinc  sul- 
phide is  a  reducing  one,  sulphuretted  hydrogen  and 
metallic  zinc  being  formed.  Metallic  zinc  is  again  con- 
verted into  zinc  oxid,  and  the  color  of  the  metallic  zinc 
mixed  with  the  other  bases  gives  the  gray  shade  that  is 
apparent.  The  manufacture  of  a  lithopone,  therefore, 
that  would  not  darken,  by  producing  an  oxid  film  and 
keeping  the  oxid  content  above  3  and  below  5  per 
cent,  would  have  its  disadvantages,  for  in  a  rosin  var- 
nish or  an  acid  resin  varnish  livering  would  eventually 
take  place,  and  one  of  the  principal  features  of  lithopone 
has  been  that  an  acid  resin  or  rosin  varnish  could  be 
used  and  no  chemical  reaction  would  take  place. 

The  large  use  of  lithopone  today  is  for  flat  wall  paints, 
for  it  can  be  mixed  with  the  China  wood  oil-rosin  var- 


52  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

nishes  without  the  danger  of  livering  or  hardening,  and 
it  has  every  advantage  as  far  as  hiding  power  and  freedom 
from  mechanical  defects  that  white  lead  and  zinc  oxid 
have,  with  the  added  advantage  of  being  non-poisonous 
(although  the  danger  of  using  a  poisonous  material  on  a 
wall  is  largely  overestimated).  Lithopone  is  likewise 
very  largely  used  in  the  cheaper  grades  of  enamel  paints. 
As  an  interior  white,  a  first  coat  white,  or  as  a  pigment 
in  the  lighter  shades  for  floor  paints,  lithopone  cannot  be 
excelled  for  its  body,  durability,  hardness,  fineness  of 
grain,  and  ease  of  application.  It  does  not  oxidize 
progressively,  and  this  single  feature  has  made  it  inval- 
uable to  the  table  oilcloth  and  floor  oilcloth  industry 
throughout  the  world.  Its  indiscriminate  use,  however, 
is  not  to  be  recommended,  and  the  paint  chemist  should 
be  permitted  to  decide  when  its  value  is  the  greatest. 
As  a  marine  interior  paint,  either  as  a  first  coat  or  for 
making  neutral  paints  where  other  whites  would  be  nec- 
essary, it  is  found  to  outlast  both  zinc  oxid  and  lead 
carbonate. 


CHAPTER  III 

THE  OXIDS  OF  LEAD 

THE  oxids  of  lead  used  in  making  mixed  paints  are 
principally  litharge,  which  is  PbO,  and  red  lead  or  orange 
mineral,  Pb3O4. 

LITHARGE 
Chemical  Formula,  PbO;  Specific  Gravity,   9.2  to  9.5 

Litharge  is  the  first  oxid  of  lead;  that  is  to  say,  when 
lead  is  melted  and  heated  in  a  current  of  air  the  first  oxid 
produced  is  the  PbO,  yellow  in  color,  and  known  as 
litharge.  Very  pure  litharge  has  the  color  of  pale  ochre. 

Litharge  in  the  manufacture  of  preservative  paints 
has  excellent  protective  qualities,  because  it  is  basic  and 
resists  corrosion.  Furthermore,  litharge  and  linseed  oil 
make  a  very  hard  cementitious  film  which  withstands 
abrasion,  but  unfortunately  litharge  combines  with  lin- 
seed oil  so  rapidly  that  when  used  in  mixed  paints  to 
any  great  extent  it  tends  to  "liver"  and  saponify.  On 
the  other  hand,  a  number  of  black  paints  which  are 
composed  of  lampblack,  carbon  black,  charcoal,  or  a  mix- 
ture of  these,  are  held  together  by  the  use  of  litharge,  and 
where  these  paints  are  used  within  a  month  or  two  after 
they  are  made  they  serve  their  purpose  perfectly. 

Litharge  is  soluble  in  acetic  acid,  and  the  other 
impurities  in  it  are  generally  insoluble,  so  that  a  very 
rapid  test  can  be  made  from  the  paint  manufacturer's 
point  of  view  by  simply  boiling  in  acetic  acid.  Litharge 
varies  in  texture  under  the  microscope,  as  is  shown  in 
the  accompanying  photomicrographs. 

S3 


54  CHEMISTRY  AND   TECHNOLOGY  OF   PAINTS 

Flake  litharge  is  generally  used  by  varnish  makers  or 
oil  boilers  for  making  drying  oil,  but  the  more  finely 
powdered  forms  of  litharge  have  a  peculiar  construction, 
and  when  the  litharge  is  impure  and  contains  metallic 
lead  and  red  lead  it  is  distinctly  noticeable  under  the 
microscope. 

RED  LEAD 
Chemical  Formula,  PhsC^;  Specific  Gravity,  9.0 

Red  lead  is  a  very  heavy  orange-red  pigment,  more  or 
less  crystalline  in  structure.  It  is  prepared  by  heating 
litharge  to  a  temperature  of  600°  to  700°  F. 

Owing  to  the  conditions 
r2$V    "'  '£•**£&'•  under  which  it  is  made  it 

c*  .  '  •    '* 

>f>v  -t />*'>*  contains   from  a  trace   to 

/&>'  -  >  vk 

.   .^     an  appreciable  percentage 

:\f^    of     litharge     (PbO),     and 

LS ;%-V '•£"*£.  ' «S£Av  when  used  for  paint  pur- 

lirv;^'^V'V^'  'r^J  poses    it    cannot    be    said 

V-;.  '  •    f  *";•;/ •*'*''r/>* "**•: A  •     that    a    small    content    of 

'^•j-  •'"  V'^  Vs*.1.},*     .. 
^  '^'''-t\''*''^:^y^'^-'^*^j}'      litharge    does    any   harm. 

<&&*?#-**•£&£$&*$?*•''         When  prepared  in  linseed 

^'v^"''^^ikv'\r^i^  j?"  *'»"»' ' 

H*-?'^*1^^^'  oil  it  must  be  freshly  used, 

-^.i^.^jV^-^  .  .  ' 

otherwise    it  forms  a  dis- 

No.  1 1 .  LITHARGE — Photomicrograph  xioo.     .  .  . 

tmct  combination  with  lin- 
seed oil  and  becomes  hard  and  unfit  for  use.  In  its 
physical  characteristics  it  can  be  compared  with  plaster 
of  paris.  It  acts  very  much  like  plaster  of  paris  when 
mixed  with  water.  Once  set,  it  may  be  reground  and  will 
never  set  again.  Its  use  as  a  priming  coat  for  structural 
steel  has  been  enormous,  but  engineers  who  have  studied 
the  subject  have  come  to  the  conclusion  that  there  are 
other  materials  just  as  good,  or  better,  which  are  easier 
to  apply  and  do  not  possess  the  characteristic  difficulties 


THE  OX  IDS  OF  LEAD 


55 


of  application.  The  author  has  made  many  investigations 
on  this  subject,  and  for  further  detail  would  refer  the  reader 
to  the  Journal  of  the  Society  of  Chemical  Industry, 
Vol.  XXI,  January,  1902,  and  Vol.  XXIV,  May,  1905. 

There  are  some  manufacturers  in  the  United  States 
who  make  red  lead  from  litharge  and  use  nitrite  of  soda 
as  an  oxidizing  material,  and  in  the  manufacture  of  this 
type  of  red  lead  carelessness  in  manufacture  will  result 
in  a  fairly  large  percentage  of  caustic  soda  remaining  in 
the  red  lead.  Caustic  soda  finds  its  way  frequently  into 
litharge  when  it  is  made 
by  what  is  known  as  the 
nitrate  process,  in  which 
nitrate  of  soda  and  me- 
tallic lead  are  fused  to- 
gether, yielding  an  oxid  of 
lead,  PbO,  and  nitrite  of 
soda,  NaNOo.1  Red  lead 
manufactured  by  this  pro- 
cess  will  usually  contain  a 
small  amount  of  caustic 
soda  and  nitrite  of  soda, 
and  such  red  lead,  al- 
though otherwise  pure,  makes  a  very  poor  paint,  because 
the  ca*ustic  soda  saponifies  the  linseed  oil,  and  exposure 
to  weather  of  a  few  months  will  turn  the  red  lead  wiiite 
or  pinkish  white  and  make  it  very  soluble  in  rain  water. 
Rust  is  also  rapidly  produced  under  such  red  lead,  and 
therefore  in  specifying  red  lead  it  is  well  for  the  engi- 
neer to  insert  a  clause  that  an  aqueous  mixture  of  red 
lead  shall  show  no  reaction  with  phenolphthalein. 

Within  the  last  five  years  a  great  improvement  has 
been   made   in   the   manufacture   of   red   lead,    and   this 

1   See  Holly's  "Analysis  of  Paint  and  Varnish,"  p.  221. 


, 

No.  12.  LITHARGE  —  Photomicrograph  X3oo. 


56  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

improved  form  has  been  known  as  Dutch  Boy  Red  Lead, 
which  is  practically  a  chemically  pure  Pb3O4.  Pure  red 
lead  was  the  one  material  which  had  never  been  sold  either 
ground  in  oil  or  ready  for  use,  owing  to  the  fact  that  the 
large  content  of  litharge  combined  with  the  fatty  acid 
of  the  oil  and  the  glycerine  and  formed  a  lead  soap.  It 
is  well  known  that  litharge  cement,  used  for  many  pur- 
poses around  a  factory,  is  litharge  and  glycerine,  which 
sets  up  hard  within  an  hour  and  forms  a  vitreous  product. 
It  is  also  well  known  that  when  linseed  oil  is  neutralized 
with  caustic  soda,  and  the  resulting  linoleate  of  soda 
soap  filtered  out,  a  ready  mixed  or  semi-paste  red  lead 
can  be  made  which  will  remain  soft  for  many  months, 
but  the  proprietary  brand  of  red  lead  just  referred  to 
manufactured  by  the  National  Lead  Company,  is  a  pure 
red  lead  similar  in  composition  to  orange  mineral,  which 
remains  soft  and  produces  a  paint  that  has  many  advan- 
tages over  the  old-fashioned  red  lead. 

Many  engineers  and  shipbuilders  prefer  to  use  dry 
red  lead,  and  a  proper  specification  for  dry  red  lead 
should  be  one  that  will  contain  the  minimum  amount 
of  litharge. 

It  cannot  be  denied  that  red  lead  is  one  of  the  best 
priming  materials  that  we  have,  but  under  no  circum- 
stances should  less  than  28  Ibs.  of  dry  red  lead  be  mixed 
with  one  gallon  of  linseed  oil.  Many  of  the  bad  effects 
and  failures  of  red  lead  are  not  due  to  the  lead  itself, 
but  to  bad  application  and  insufficient  dry  materials. 
As  a  matter  of  fact,  the  best  results  with  red  lead  are 
obtained  (in  the  author's  experience)  by  using  33  Ibs. 
and  one  gallon  of  linseed  oil.  To  this  oil  may  be  added 
one  half  pint  of  any  good  Japan  drier. 

As  a  priming  coat  red  lead  possesses  excellent  pre- 
servative qualities,  providing  it  be  properly  applied  within 


THE  OX  IDS  OF  LEAD 


57 


a  reasonable  time.  If  red  lead  be  used  in  the  proportion 
of  17  Ibs.  to  one  gallon  of  linseed  oil  it  forms  a  very  poor 
coating  on  account  of  the  separation  of  the  pigment 
from  the  oil,  particularly  on  a  vertical  surface.  In  a 
pamphlet  published  by  a  manufacturer  a  large  number  of 
precautions  were  given  to  the  consumer  for  the  prepara- 
tion of  red  lead  as  a  priming  coat,  the  neglect  of  any 
one  of  which  might  produce  failure  for  the  paint.  As  a 
prominent  engineer  remarked,  he  did  not  care  to  specify 
a  paint  in  which  there 
were  seventeen  chances 
of  its  failure  due  to  a 
possible  fallibility  of  hu- 
man nature.  The  use  of 
a  dry  pigment  mixed  with 
oil  and  applied  within  one 
hour  of  its  mixture  is  con- 
trary to  the  progress  of 
the  present  day,  when 
paints  finely  ground  by 
machinery  are  taking  the  No 
place  of  all  others.  A  dry 
pigment  stirred  by  hand 
in  a  pail  of  oil  carries  with  it  a  large  number  of  air 
bubbles  which  become  encysted  and  carry  oxygen 
and  other  gases  to  the  surface  to  be  protected.  The 
engineer  should,  therefore,  not  specify  that  a  paint  be 
made  entirely  of  red  lead  and  linseed  oil  and  sent  ready 
for  use  to  the  place  of  application  when  such  specifica- 
tions cannot  be  reasonably  executed.  On  the  other 
hand,  where  red  lead  is  specified  the  engineer  or  paint 
manufacturer  who  can  supply  a  material  containing 
between  40  and  50  per  cent  red  lead  and  50  and  60 
per  cent  inert  base  is  delivering  a  far  better  article, 


FRENCH  ORANGE  MINERAL  — 
Photomicrograph  X25O,  not  very  uni- 
form in  grain. 


CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 


which  can  be  more  easily  applied  than  the  undiluted  red 
lead  alone. 

The  author  made  a  large  number  of  experiments  on 
red  lead  mixed  with  linseed  oil  containing  a  small  per- 
centage of  drier,  applying  these  mixtures  to  steel.  The 
mixture  was  first  applied  the  moment  it  was  thinned,  and 
then  at  short  intervals,  up  to  the  moment  the  red  lead 
began  to  combine  with  linseed  oil  so  as  to  make  it 
impossible  to  handle  the  brush.  The  results  of  the  experi- 
ment showed  that  freshly 
applied  red  lead  was  not 
as  good  as  it  was  if  applied 
one  hour  after  it  was  mixed. 
The  paint  with  which  these 
experiments  were  made  con- 
tained 24  Ibs.  red  lead  to 
one  gallon  of  paint,  which  is 
approximately  equal  to  33 
Ibs.  dry  red  lead  to  one 
gallon  of  oil.  The  difficulty 

No.    14.    RED   LEAD  -  Photomicrograph   in     Dandling     paint    of     this 

X2oo  of  paint  film  freshly  applied,  kind   is  very  great,   owing 

showing    separation    of    the    pigment    to    the    excessive    Weight    of 
from  the  oil. 

the  paint  as  carried  by  the 

brush.  Structural  iron  painters  all  complain  that  muscular 
fatigue  ensues  where  undiluted  red  lead  is  used,  and  when 
the  inspector  is  not  watching  they  will  surreptitiously 
add  an  excessive  quantity  of  oil,  or  volatile  thinner, 
in  order  to  lighten  their  labor,  and  for  this  reason  red 
lead  has  frequently  failed,  when  as  a  matter  of  fact  it 
would  have  proved  a  perfect  success  had  the  original 
specifications  been  adhered  to.  On  the  other  hand,  there 
should  be  no  need  of  using  a  protective  paint  involving 
such  great  difficulties  when  there  are  dozens  of  others 


THE  OX  IDS  OF  LEAD 


59 


that  are  as  good,  not  only  from  the  standpoint  of  pro- 
tective influence  but  also  on  account  of  the  ease  of 
mechanical  application. 

It  has  been  mentioned  by  many  writers  that  one  of  the 
serious  defects  of  red  lead  is  the  ease  with  which  it  is 
attacked  by  sulphur  gases,  but  this  objection  does  not 
hold  good  where  it  is  properly  and  quickly  coated  over 
with  a  protective  coat  of  the  bituminous  class.  That 
red  lead  in  its  pure  or  concentrated  state  is  not  as  good 
as  a  paint  containing  a  solid 
diluent  has  been  shown  time 
and  again  where  silica, 
lampblack,  graphite,  silicate 
of  alumina,  and  such  lighter 
pigments  were  mixed  with 
it.  Its  extraordinarily  high 

>r  -.       •  i 

specific  gravity  is  very  much 
against  its  use  as  a  paint, 
but  if  a  mixture  of  one 
pound  red  lead  and  one 
pound  wood  black  is  taken 

No.    15.   RED   LEAD  —  Photomicrograph 
the  average   Specific   gravity 

Of  the  tWO  is  equal    to  that 
.  . 

of  zinc  oxid.  Its  spreading 
and  lasting  power  is  increased,  so  that  a  mixture  of 
this  kind  is  equal  to  a  mixture  of  any  of  the  good  pre- 
pared paints  for  structural  steel.  Two  large  exposure 
tests  made  by  the  author  in  1899  and  examined  in  1905 
showed  that  a  mixture  of  50  per  cent  red  lead  and 
50  per  cent  graphite  ground  fine  and  mixed  in  a  pure 
linseed  oil  containing  5  per  cent  of  lead  drier  wore  almost 
as  well  as  a  mixture  of  75  per  cent  Fe2O3  (ferric  oxid), 
20  per  cent  silica,  and  5  per  cent  calcium  carbonate. 
The  former  paint,  when  the  hand  was  rubbed  over  it, 


,  applied  one  hour  after  mixing, 
showinS  seParation  and  air  bells  en- 
cysted  in  film. 


60  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

showed  slightly  more  destruction  of  the  oil,  the  graphite 
giving  a  stove  polish  effect  on  the  hand.  The  latter 
paint  also  showed  a  very  slight  stain  on  the  hand,  but  not 
quite  as  marked  as  the  former.  The  metal  underneath 
both  was  in  a  good  state  of  preservation,  three  coats  of 
paint  having  been  applied.  The  exposure  was  made 
on  a  slanting  roof  in  New  York  City. 

Red  lead  has  had  the  great  advantage  of  having  been 
the  first  protective  paint  ever  used,  for  years  no  better 
paint  being  known.  In  this  respect  it  is  analogous  to 
white  lead.  Much  of  the  good  reputation  of  white  lead 
is  due  to  the  fact  that  for  centuries  there  was  no  other 
white  paint,  consequently  no  comparison  could  be  made. 
It  must  be  borne  in  mind  that  all  these  experimental 
researches  concerning  red  lead  are  based  on  very  fine  red 
lead,  and  no  consideration  is  given  to  the  detrimental 
reports  concerning  red  lead  due  to  the  fact  that  it  was 
improperly  made  and  coarse. 

A  laboratory  test  of  red  lead  always  shows  up  remark- 
ably well.  A  steel  saucer  painted  with  red  lead  in  the 
laboratory  will  demonstrate  that  this  pigment  is  superior 
to  many  others,  but  a  field  test  of  material  made  accord- 
ing to  a  laboratory  formula  and  applied  on  several  tons 
of  steel  will  generally  show  the  opposite,  for  the  obvious 
reason  that  in  the  laboratory  a  small  test  is  usually 
carefully  applied  and  little  exertion  is  necessary,  either 
with  the  mixing  of  material  or  for  its  application.  The 
temperature  conditions  of  the  laboratory  being  normal, 
the  person  who  mixes  the  paint  usually  scrutinizes  the 
result  carefully.  On  the  other  hand,  in  the  field  or  at 
the  shop  a  brush  is  used  which  will  do  the  greatest 
amount  of  covering  with  the  least  amount  of  exertion. 
The  mixture  may  not  be  made  by  the  best  possible  for- 
mula, and,  if  it  is,  more  thinning  material  is  generally 


6i 

added  until  it  works  freely.  The  vertical  part  of  the 
surface  will,  on  account  of  its  position,  be  more  difficult 
to  cover,  and  the  paint  will  sag  or  run  from  it;  whereas, 
the  flat  plate  or  saucer-shaped  cup  used  in  the  laboratory 
holds  the  material  in  place  by  virtue  of  its  position. 

'BLUE  LEAD 

In  the  sublimation  of  Galena  a  peculiar  sulphide  of 
lead  is  produced,  which  has  been  known  commercially 
as  blue  lead,  on  account  of  its  blue-gray  appearance. 
This  product  has  been  on  the  market  for  several  years. 
The  contention  is  that  sulphur  fumes  do  not  affect  it  as 
they  affect  red  lead.  As  a  priming  coat  it  has  been  well 
spoken  of.  Its  composition  is  as  follows: 

Carbon 2.25 1.73 

Lead  Sulphate 52.92 49-79 

Lead  Sulphite .36 1.44 

Lead  Sulphide 4.55 4.93 

Lead  Oxid 37-48 41-34 

Zinc  Oxid 2.45 i.oo 

100.01  100.23 

No  truly  representative  analysis  of  this  material  can 
be  given,  owing  to  the  variation  in  the  amount  of  sul- 
phate, sulphite,  and  sulphide.  The  material  is  not  very 
fine;  in  fact,  it  contains  an  appreciable  amount  of  grit, 
which,  however,  is  removed  in  the  second  grinding. 

The  pigment  is  not  permanent  to  light,  but  in  all 
probability  this  change  in  its  tone  is  due  to  a  chemical 
rather  than  to  a  physical  decomposition. 


CHAPTER  IV 

THE  RED  PIGMENTS 

THE  red  pigments  used  in  the  manufacture  of  mixed 
paints  are  principally  the  oxids  of  iron,  the  red  oxids 
of  lead,  and  the  permanent  vermilions.  No  space  will 
be  devoted  to  the  sulphide  of  mercury  (quicksilver  ver- 
milions), as  the  use  of  these  materials  has  been  super- 
seded entirely  by  aniline  or  para-nitraniline  vermilion. 
Likewise  no  attention  will  be  paid  to  the  sulphide  of  an- 
timony reds,  as  they  are  obsolete  in  paint  manufacturing. 

Among  all  the  red  pigments  in  the  paint  industry 
the  oxids  of  iron  take  the  lead  as  by  far  the  most  useful. 
Several  years  ago  the  author  called  attention  to  the  fact 
that  various  forms  of  ferric  oxid  having  the  formula 
Fe203  could  be  used  as  rubber  pigments.  The  sulphur 
used  in  the  vulcanizing  of  rubber  had  no  effect  on  the 
ferric  oxid,  no  sulphide  of  iron  being  formed  in  the  com- 
bination. On  investigation  it  was  found  that  some  forms 
of  ferric  oxid  are  remarkably  stable  in  composition,  acting 
in  many  regards  like  a  spinel.  Exhaustive  tests  made 
with  some  of  the  ferric  oxids  used  as  paints  for  the  pro- 
tection of  steel  and  iron  show  that  they  are  far  superior 
to  red  lead  and  to  graphite  as  paint  protectives,  being 
midway  between  the  two  in  specific  gravity.  A  mixture 
of  graphite  and  ferric  oxid  (containing  75  per  cent  Fe2O3 
and  25  per  cent  silica)  outlasted  graphite  by  two  years 
and  red  lead  by  three  years.  These  tests  were  made  on 

horizontal  roofs,  and  eliminating  the  question  of  the  cost 

62 


THE  RED  PIGMENTS  63 

of  the  paints,  the  ferric  oxid  stood  the  test  and  was  the 
cheapest  in  the  end.  No  argument  can  be  adduced  that 
ferric  oxid  is  a  carrier  of  oxygen,  for  it  is  a  complete 
chemical  compound,  is  not  readily  acted  upon  by  dilute 
acids,  not  affected  by  alkalis  nor  by  sulphur  gases,  and 
as  a  paint  the  author  has  not  been  able  to  demonstrate 
that  it  reacts  on  linseed  oil. 

All  of  these  arguments  refer,  of  course,  to  a  ferric 
oxid  of  known  purity  and  definite  composition  either  as 
pure  Fe2O3  or  as  Fe2O3  containing  25  per  cent  of  silica. 
In  the  course  of  its  manufacture  from  the  waste  products 
of  wire  mills,  for  instance,  or  direct  from  ferrous  sulphate, 
the  processes  being  analogous,  there  is  a  likelihood  that 
a  small  percentage  of  free  sulphuric  acid  may  cling 
mechanically  to  the  substance.  A  good  sample  boiled 
with  water  and  tested  with  methyl  orange  will  demon- 
strate this  defect.  It  is  wise,  therefore,  under  all  cir- 
cumstances to  add  up  to  5  per  cent  calcium  carbonate 
in  any  or  all  of  these  ferric  oxid  paints.  There  is,  how- 
ever, another  ferric  oxid  made  from  Persian  ore.  Over 
one  hundred  analyses  of  this  ore  in  the  laboratory  of  the 
author  have  shown  that  its  composition  will  not  vary 
more  than  2  per  cent  either  way,  it  being  75  per  cent 
Fe203  and  25  per  cent  Si02. 


VENETIAN  REDS 

Venetian  reds  have  sometimes  been  described  as  burnt 
ochres,  but  this  definition  of  the  Venetian  reds  is  incor- 
rect. The  generally  accepted  composition  of  the  Venetian 
red  is  a  combination  of  ferric  oxid  and  calcium  sulphate, 
in  which  the  ferric  oxid  will  run  from  20  to  40  per  cent, 
and  the  calcium  sulphate  from  60  to  80  per  cent.  When 
ferrous  sulphate  is  heated  with  lime  an  interchange  or 


64  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

reaction  takes  place,  the  sulphuric  acid  of  the  copperas 
going  to  the  lime  while  an  oxidation  of  the  iron  takes 
place.  Another  method  known  as  the  wet  method  is 
the  direct  reaction  between  ferrous  sulphate  and  wet 
slacked  lime. 

Venetian  red  has  been  known  as  a  paint  pigment  for 
upwards  of  a  century,  and  while  theory  would  indicate 
that  it  is  by  no  means  as  desirable  a  pigment  to  use  as 
other  mixtures  of  ferric  oxid,  it  must  be  apparent  that 

in  view  of  the  fact  that  it 
has  given  general  satisfac- 
tion it  is  by  no  means  as 
undesirable  a  pigment  as 
chemists  indicate.  The  ten- 
<   dency,    however,    at     the 
'•j   present  time  is  for  manu- 
./     facturers    to     buy    strong 
pure     oxids     and     reduce 
them     with     other     inert 
fillers,    for    the    principal 
NO.   16.    ENGLISH    VENETIAN    RED  —  reason  that  a  Venetian  red 
Photomicrograph  X25o,  showing  cai-  carrying  a  high  percentage 

cium    sulphate   crystals.  ,       ,    . 

of  calcium  sulphate  and  an 

unknown  quantity  of  water  or  moisture  tends  to  become 
hard  in  the  package,  whereas  the  mixtures  of  known 
composition  remain  soft  for  many  years.  Venetian  reds 
are  all  of  the  familiar  brick  color  shade,  the  color  of 
bricks  being  caused  by  the  same  pigment  as  the  one  that 
gives  the  color  to  Venetian  red. 

INDIAN  RED 

This  is  supposed  to  have  been  named  by  Benjamin 
West,  a  celebrated  American  artist  who  lived  more  than 
a  century  ago,  and  who  as  a  boy  used  a  few  primary 


THE  RED  PIGMENTS 


earth  colors  as  pigments  for  paint.  One  of  these  was  a 
natural  hematite,  and  he  observed  that  the  Indians  used 
this  for  painting  their  faces.  The  name  is  also  supposed 
to  have  had  its  origin  in  the  fact  that  "Persian  Gulf 
Ore,"  which  was  found  in  the  Orient,  was  exported  to 
England  under  the  name  of  "East  Indian  Red."  This 
Persian  Gulf  Ore  is  likewise  a  hematite,  and  later  on  a 
similar  ore  was  found  in  parts  of  England  which,  when 
mined,  looked  very  much  like  coal,  but  when  crushed  and 
ground  in  water  turned 
a  deep  blood-red.  The 
old  name  for  this  mineral 
is  still  "blood-stone,"  and 
some  very  fine  specimens 
of  this  mineral  are  still 
mined  in  England  in  con- 
junction with  beautiful 
quartz  crystals,  so  that 
we  find  in  England  a  care- 
ful selection. 

The  native  Indian  red  NO.  17.  AMERICAN 
will  run  90  per  cent  Fe2O3, 
the  American  88  per  cent, 
and  the  Persian  75  per  cent,  the  balance  in  every  case 
being  silica.  The  Indian  red  of  commerce,  however,  is 
an  artificial  product  made  like  the  base  of  the  Venetian 
red  by  calcining  copperas  and  selecting  the  product  as 
to  shade.  There  is  no  pigment,  with  possibly  the  excep- 
tion of  lithopone  and  artificial  barium  sulphate,  which  will 
approach  Indian  red  in  fineness  of  grain.  The  prices 
which  a  fine,  pure  Indian  red  or  ferric  oxid  of  any  shade 
will  command  are  most  remarkable,  many  tons  being  sold 
every  year  in  large  quantities  at  as  high  a  price  as  fifty 
cents  per  pound  and  used  entirely  for  polishing  gold, 


VENETIAN  RED  — 
Photomicrograph  X250,  showing  fine 
grains  of  calcium  sulphate. 


66 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


silver,  and  other  metals.     The   well-known  "watch-case 

rouge"  is  nothing  but  pure  Indian   red  which  has  been 

ground,  washed,  and  treated  mechanically  with  so  much 

care    that   three-quarters   of   its    selling    price    is    repre- 

^  sented  in  the  labor  of  manip- 

.      v        '     -,  •  :    -  ulation.     If,  therefore,  fine 

*     •  *  f* 

.   "       '*.  'ii     Tk~*   *•*        ferric  oxid  be  mixed  with 

linseed  oil  it  can  be  easily 
seen  from  the  nature  of  the 
physical  characteristics  of 
i1  the  pigment  that  a  remark- 
ably good  result  is  obtained. 


• «» 


v» 

:»- 


PERMANENT  VERMILION 

'••.  •«  •  It  may   be    of    interest 

NO.  18.  AMERICAN  HEMATITE  —  Photo-   to  the  chemist  unacquainted 

micrograph  X25O,  showing  a  few  large     with     the     manufacture      of 

dry   colors   to    know    that 

English  vermilion  (sulphide  of  mercury),  of  which  the  proto- 
types are  Chinese  vermil- 
ion, American    quicksilver 
vermilion,    etc.,    was    for- 
merly used  wherever  a  per- 

j 

manent  red  was  desired;  ; 
and  particularly  for  rail-  I 
road  work  was  this  ver-  I 

N 

milion  the  only  red  that 
could  be  used,  for  it  did 
not  fade.  It  has,  however, 
the  disadvantage  of  dark- 
ening in  the  light  and 
eventually  turning  brown. 
The  real  sulphide  of  mer- 
cury is  black,  and  red  sulphide  of  mercury  is  a  forced 
compound.  The  mineral  cinnabar,  which  has  the  com- 


No.  19.  INDIAN  RED  -  -  Photomicro- 
graph X3oo,  98  per  cent  Fe^Oa,  very 
fine  uniform  grain. 


THE  RED  PIGMENTS  67 

position  just  described,  is  also  red,  but  not  very 
bright,  and  that  found  and  made  in  Austria,  known 
as  Trieste  vermilion,  has  always  been  regarded  as  the 
most  permanent  of  these  sulphide  of  mercury  reds. 
Mixed  paint  manufacturers  do  not  use  it,  and  in  fact 
paint  manufacturers  generally  have  discarded  it,  for  the 
reason  that  the  so-called  para-nitraniline  reds  are  better, 
cheaper,  and  more  permanent. 

In  order  that  the  chemist  may  understand  the  com- 
position of  the  para-vermilions,  a  complete  formula  is 
given  for  their  manufacture. 

REACTIONS  INVOLVED  IN  MAKING  PARA-RED 
Part  i.     (Solution  of  Para-nitraniline  and  Diazotizing.) 

NO2  NO2 

C6H4         +2HC1  =      C6H4        .2HC1 
NH2  NH2 

(para-nitraniline)  (para-nitraniline  hydrochloride) 

N02  NO2 

C6H4         .2HC1  +  NaNO2  =  C6H4  +  NaCl  +  2H20 

NH2  N :  NCI 

(benzene  nitro-azochloride) 

Part  2.     (Beta-naphthol  Solution.) 

CioH7OH     +      NaOH     -      Ci0H7ONa     +      2H2O 
(beta-naphthol)  (sodium  beta-naphtholate) 

Part  j.     (Mixing  of  No.  i  and  No.  2  to  Produce  Color.) 

N02 
C6H4  +  CioH7ONa 

N:  NCI 
(benzene  nitro-azochloride)      (sodium  beta-naphtholate) 

NO2 

=       C6H4  +      NaCl 

N:  NCioHeOH 
(Para  Red) 


68  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

PARA-NITRANILINE  LAKE 
NAPHTHOL  SOLUTION 

15  grams  beta-naphthol  or  beta-naphthol  R.;  30  grams  caustic 
soda  lye  22°  Be.;  10-20  grams  para-soap  P.  N.  (In  sufficient 
boiling  water  to  dissolve  thoroughly). 

DIAZO  SOLUTION 

14  grams  para-nitraniline  dissolved  in  boiling  water;  25  grams 
hydrochloric  acid  20°  Be.;  200  grams  ice. 

When  the  solution  is  cooled  to  32°  to  35°  F.,  add  very  slowly, 
while  stirring  constantly,  34  grams  nitrite  of  soda  solution  (29  gms. 
nitrite  in  100  gms.  cold  water). 

Allow  to  stand  15  to  20  minutes.  Then  add  slowly  35  grams 
acetate  of  soda  previously  dissolved  in  cold  water. 

To  the  naphthol  solution  add  the  base  you  intend  to  use.  250 
grams  of  blanc  fixe  give  good  results.  For  bluer  shades  use  beta- 
naphthol  R.  For  yellower  shades  use  beta-naphthol. 

When  these  colors  have  been  precipitated  on  an 
orange  mineral  base  they  have  been  known  to  catch  fire 
spontaneously  in  the  drying  room,  and  therefore  great 
care  should  be  exercised  in  their  manipulation  with  lead 
bases. 

There  appears  to  be  a  difference  of  opinion  among 
consumers  as  to  whether  these  reds  are  really  permanent 
or  not.  Careful  investigation  reveals  the  following: 
The  para-vermilions  are  soluble  in  linseed  oil,  and  there- 
fore even  when  a  pigment  contains  only  5  per  cent 
tinctorial  matter  it  is  useful  and  effective  as  a  red  paint. 
White  lead  in  any  form  mixed  with  a  para-red  destroys 
its  color  and  turns  it  brown.  A  few  years  ago  when  this 
color  first  appeared  on  the  market  it  frequently  hap- 
pened that  it  turned  perfectly  white  when  exposed  to  the 
air,  but  when  it  was  rubbed  with  raw  linseed  oil  it  turned 
a  brilliant  red  again,  and  a  microscopic  examination 


THE  RED  PIGMENTS  69 

showed  that  the  film  had  been  entirely  incrusted  with 
very  fine  crystals  of  sodium  nitrite  and  other  salts  that 
had  not  been  completely  washed  out  of  the  lake  pigment, 
and  so  para-red  obtained  a  bad  reputation,  not  due  to 
the  color,  but  due  to  the  ignorance  of  the  manufacturer. 

Para-red  has  penetrative  powers  in  both  directions; 
when  painted,  for  instance,  on  a  sheet  of  cloth  for  sign 
work  it  will  penetrate  through  and  stain  the  under  side 
yellow.  If  white  lead  paint  be  lettered  over  it,  it  acts 
the  same  and  turns  white  lead  yellow  or  a  yellowish 
brown. 

Enormous  quantities  of  this  vermilion  are  made  every 
year,  and  so  strong  is  this  color  that  average  analyses 
of  the  paint  used  for  agricultural  implement  purposes 
will  show  the  pigment  to  be  composed  of  90  per  cent 
barytes,  5  per  cent  para-red,  and  5  per  cent  zinc  oxid  or 
zinc  sulphide.  Its  presence  in  mixed  paints  is  very  easily 
detected  by  boiling  with  varnish  solvents  and  noting  the 
peculiar  orange  color  of  the  filtrate. 

HELIO  FAST  RED 

This  is  also  known  as  Harrison  Red,  and  is  perhaps 
one  of  the  most  permanent  pigments  that  we  have  of 
the  vermilion  type.  It  is  made  from  nitro-paratoluidine, 
and  in  tinctorial  strength  is  practically  ten  times  stronger 
than  a  quicksilver  vermilion.  It  dries,  however,  very 
badly,  and  when  a  sufficient  percentage  of  strong  drier 
such  as  a  resinate  of  lead  and  manganese  is  added,  the 
color  tends  to  darken  slightly  on  exposure.  This  color 
does  not  bleed,  and  it  is  apparently  insoluble  in  drying 
oil;  nor  does  it  turn  a  white  pigment  into  a  brown,  as 
is  the  case  with  the  para-reds.  When  this  pigment  is 
mixed  or  reduced  with  a  large  quantity  of  whiting, 
barytes,  or  other  white  base,  and  exposed  to  the  air  it 


70  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

apparently  fades,  and  on  close  examination  this  fading 
is  found  to  be  washing  out  of  the  pigment  itself  and  the 
exposure  of  the  base  upon  which  it  is  made,  so  that  the 
conclusion  we  must  arrive  at  as  regards  the  permanency 
of  this  remarkable  color  is  that  when  used  in  sufficient 
strength  it  is  permanent,  but  when  diluted,  reduced,  or 
adulterated  to  too  great  an  extent  the  base  upon  which 
it  is  made  overpowers  or  masks  the  permanent  pigment 
itself. 

LITHOL  RED 

This  is  2-naphthylamine-i-sulphonic-acid-diazo-beta 
naphthol,  and  is  sold  to  color  manufacturers  in  paste 
form  as  a  semi-finished  color. 

In  the  manufacture  of  permanent  vermilion  the  fol- 
lowing is  the  method  of  procedure: 

The  paste  color  is  mixed  with  the  desired  amount  of 
base  (blanc  fixe,  clay,  barytes,  whiting,  etc.)  and  water 
until  a  thin,  uniform  suspension  is  obtained.  Barium 
chloride  to  the  extent  of  10%  of  the  paste  color  is  then 
added  and  the  whole  steamed  for  about  \  hour  until 
the  shade  is  fully  developed.  The  color  is  then  washed 
once  or  twice,  pressed,  and  dried. 

Lithol  red  has  the  advantage  over  para-nitranilines 
in  that  it  does  not  bleed,  and  that  it  does  not  turn  dark 
upon  exposure.  It  is  very  largely  used  in  the  manu- 
facture of  permanent  railway  signal  reds,  and  when  not 
reduced  or  diluted  with  too  much  clay  and  barytes  is 
permanent,  but  when  it  contains  an  excess  of  the  so- 
called  reenforcing  pigments  it  washes  out  and  fades. 


CHAPTER  V 

THE  BROWN  PIGMENTS 

THE  principal  brown  pigments  used  in  the  manu- 
facture of  paint,  excepting  the  aniline  lakes,  are  the  burnt 
siennas,  the  burnt  umbers,  burnt  ochres,  Prince's  Metallic 
or  Princess  Mineral  brown  and  Vandyke  brown. 

The  burnt  siennas,  whether  they  are  American  or 
Italian,  are  a  translucent  form  of  ferric  oxid  and  clay. 
In  other  words,  when  the  hydrated  oxid  of  iron  and  clay 
mineral  are  burnt  ferric  oxid  is  the  result,  and  the  clay 
remains  unaltered,  any  water  in  combination,  of  course, 
being  driven  off.  If  the  resulting  color  is  translucent 
and  is  of  the  nature  of  a  stain  we  call  it  a  sienna,  but  if 
the  resulting  color  is  opaque  and  of  the  nature  of  a  paint 
we  call  it  an  oxid. 

The  umbers  are  similar  in  composition  to  the  siennas, 
with  the  exception  that  they  all  contain  manganese  and 
are  of  a  much  deeper  brown  and  do  not  approach  the  red. 

The  Princess  Mineral  brown  or  Prince's  Metallic 
oxids  are  calcined  carbonates,  silicates,  and  oxids  only 
found  in  America,  and  are  very  largely  used,  particularly 
for  the  painting  of  wood. 

Vandyke  brown  is  a  very  deep  brown,  and  is  trans- 
lucent when  finely  ground,  containing  more  than  50  per 
cent  of  organic  matter. 

AMERICAN  BURNT  SIENNA 

This  is  a  permanent  reddish  brown  pigment  made  by 
calcining  raw  sienna,  raw  sienna  being  a  hydrated  oxid 
of  iron  containing  clay.  When  burnt  the  percentage  of 

71 


72  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Fe203,  or  ferric  oxid,  ranges  from  25  to  60  per  cent, 
depending  upon  the  original  ore.  There  is  one  grade 
found  in  the  Pennsylvania  section  which  assays  as  high 
as  80  per  cent  ferric  oxid,  and  is  known  as  double  strength 
sienna.  This  is  richer  and  deeper  than  the  Italian  sienna, 
and  when  reduced  with  ordinary  clay  and  ground  in  oil 
makes  a  staining  pigment  equal  to  the  Italian.  From  a 
raw-material  standpoint  the  Italian  siennas  when  tinted 
with  20  per  cent  of  white  show  a  bluish  tint,  whereas  the 

American  siennas  show  a 
brownish  or  yellowish  tint, 
and  only  one  who  has  had 
a  great  deal  of  experience 
in  tinting  out  these  siennas 
can  tell  empirically  the  dif- 
ference between  an  Amer- 
ican and  a  burnt  sienna. 
The  Italian  and  the  Ameri- 
can siennas  normally  con- 
tain some  calcium  salts, 

No.  20.  AMERICAN  BURNT  SIENNA-  but  occasionally  Some  ores 
Photomicrograph  X2SO,  excellent  qual-  are  foimd  which  are  free 
ity,  uniform  grain.  ,.  ,. 

from  lime  compounds.   For 

paint  purposes,  however,  these  are  no  better  than  those 
that  contain  lime,  for  many  grinders  add  from  5  to  10 
per  cent  of  whiting  to  umbers  and  siennas  to  prevent 
them  from  running  or  disintegrating  when  used  as  stain- 
ing colors. 

ITALIAN  BURNT  SIENNA 

Italian  burnt  sienna  is  made  from  raw  sienna,  the 
raw  sienna  being  a  hydrated  oxid  of  iron  containing  clay, 
in  which  the  iron  predominates,  the  burnt  sienna  being 
of  the  same  composition  minus  combined  water.  The 


THE  BROWN  PIGMENTS  73 

hydrated  oxid  of  iron  is  normally  yellow,  and  when 
this  is  burnt  the  ferric  oxid  which  is  produced  is  red- 
dish or  reddish  brown. 

Italian  burnt  sienna  differs  from  most  American 
burnt  siennas  in  that  its  ferric  oxid  content  is  generally 
greater.  The  Italian  burnt  siennas  average  from  60 
per  cent  Fe2O3  to  as  high  as  75  per  cent.  The  American 
burnt  sienna,  known  as  double  strength  sienna,  which  is 
equal  in  iron  content  to  the  Italian,  differs  totally  in 
shade,  the  American  being  of  the  order  of  an  Havana 
brown,  the  Italian  being  of  a  maroon  type. 

Siennas  in  mixed  paints  are  largely  used  for  their 
tinting  quality,  the  resulting  shade  being  a  yellowish 
maroon  or  salmon  color  of  extreme  permanence.  After 
several  years'  exposure  a  mixture  of  white  and  burnt 
sienna  will  darken  slightly,  but  will  never  fade. 

Under  the  microscope  a  finely  ground  sienna  shows 
little  or  no  grain. 

BURNT  UMBER 

Burnt  umber  is  a  very  useful  pigment,  and  is  found 
in  the  United  States  and  also  imported  from  Italy, 
Cyprus,  and  Turkey-in-Europe.  All  umbers  normally 
contain  over  5  per  cent  of  manganese  dioxid,  while 
some  of  them  contain  as  high  as  20  per  cent  manganese. 
The  Turkey  umbers  are  generally  richer  in  manganese 
than  the  American  umbers. 

A  typical  analysis  cf  burnt  Turkey  umber  would  be 
as  follows: 

Calcium  Carbonate 7  % 

Silica 34  % 

Manganese  Dioxid 14  % 

Ferric  Oxid 42  % 

Alumina 3% 

100% 


74  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

A  typical  analysis  of  an  American  burnt  umber 
would  be: 

Silica  and  Alumina  (clay) 60  % 

Ferric  Oxid 25  % 

Manganese  Dioxid 8  % 

Calcium  Carbonate 5  % 

Carbon  and  Carbonaceous  matter 2  % 

100% 

These  types  would  indicate  that  an  American  umber 
is  not  as  strong  and  does  not  contain  as  much  ferric  oxid 
and  manganese  dioxid  as  a  Turkey  umber. 

BURNT  OCHRE 

Burnt  ochre  is  distinctively  an  American  color,  and 
differs  in  physical  quality  from  burnt  sienna  in  so  far  as 
the  burnt  ochre  has  hiding  power  and  the  sienna  has  trans- 
lucent or  staining  power.  Burnt  ochre  is  more  like  a  brown 
paint,  and  burnt  sienna  like  a  mahogany  stain.  Burnt 
ochre  covers  solidly;  burnt  sienna  covers  translucently. 

Some  of  the  American  siennas  which  are  not  good 
enough  for  staining  purposes  are  burnt  and  find  their 
way  to  the  market  as  structural  steel  paints  and  railroad 
paints  of  the  brownish  red  order;  as  such  they  are  remark- 
ably good  in  their  protective  quality  against  corrosion. 

No  standard  of  composition  can  be  given,  as  burnt 
ochre  varies  very  much  in  the  percentage  of  iron,  some 
of  the  burnt  ochres  ranging  as  low  as  30  per  cent  iron 
oxid  and  others  as  high  as  70  per  cent,  the  balance  in 
both  cases  being  clay. 

PRINCE'S  METALLIC  OR  PRINCESS  MINERAL  BROWN 

This  is  one  of  the  best  known  paints,  and  has  had  a 
successful  career  for  more  than  fifty  years.  It  is  a  very 


THE  BROWN  PIGMENTS  75 

pleasing  brown  pigment,  which  has  an  enormous  use  all 
over  the  United  States  for  painting  wooden  freight  cars 
and  for  painting  tin  roofs.  Where  it  is  applied  to  a  flat 
surface  like  a  tin  roof  it  has  been  used  for  many  years 
in  its  dry  state,  and  mixed  with  half  raw  and  half  boiled 
linseed  oil  in  the  field.  It  is  at  times  fairly  fine,  and 
while  it  is  an  excellent  preservative  for  steel  it  may  be 
regarded  as  a  better  preservative  coating  for  wood,  as 
many  of  the  wooden  barns  in  the  country  in  the  States 
have  lasted  ten  years  when  coated  with  two  coats  of  this 
pigment.  The  analysis  of  the  material  varies  very  much. 

Geologically,  the  ore  is  _^ 

a  carbonate,  and  lies   be-  ,     ''  •      s     «  t 

tween    the    upper    silurian  *  \\-;&  '*„"  '  ••  •* 

^*"»  *•"*"','*'«       i    '  * 
and  lower  devonian.     It  is     /•**"'.  •.**&»*. 'v^'    » 

a  massive  mate-rial  of  bluish    ;  -•    "'.-I*-*-  %•'•$  *J% .-' '  4'*^'if4i*  '• 

*  „*    *  '.         »,."*  *•    -V* 

gray    color    when    mined,  .•  ;^-.  *    ';.-.' i$* •  »•' '  -' 

and    resembles    limestone,  '>•<.'„,         '\+  '  :>''<f»  *l:*j 

although  it  contains  a  very  \|iw  "'**«-'*'"'  '^^V.^*''.     ^ 

low    percentage    of    lime.  <(*/t 

The   process  of   mining  is  '"*, 
by    shaft- work.      The    ore 

^ 

itself  lies  between  two  hard 

•i  j  i  No.    21.   PRINCE'S    METALLIC  —  Photo- 

rocks  and  rarely  ever  ex- 

J  micrograph  X3oo. 

ceeds  three  feet  in  width, 

and  as  a  consequence  the  mining  is  an  expensive  operation. 
The  ore  is  hauled  to  the  kilns,  where  it  is  roasted, 
which  drives  off  the  carbon  dioxid  and  converts  it  into 
a  sesqui-oxid.  The  milling  is  the  ordinary  process  used 
in  grinding  any  of  the  iron  oxids. 

The  material  was  originally  manufactured  by  Robert 
Prince  of  New  York,  who  became  interested  in  a  slate 
quarry  located  in  Carbon  County,  Pennsylvania,  from 
which  locality  the  original  material  came. 


- 


76  CHEMISTRY  AND    TECHNOLOGY  OF  PAINTS 

A  fair  analysis  of  this  material  is  as  follows: 

Oxid  of  Iron  (Fe2  O3) 48.68% 

Silica , . .  33-37% 

Alumina 12.08  % 

Lime 2.02% 

Magnesia 1.25  % 

Loss  on  Ignition 2.34  % 

Undetermined 0.26  % 

100.00% 

As  the  material  is  not  alkaline,  the  lime  and  magnesia 
are  undoubtedly  combined  with  the  silica,  so  that  the 
material  other  than  oxid  of  iron  is  silicate  of  alumina, 
lime,  and  magnesia.  Sometimes,  the  percentage  of  Fe203 
will  run  below  40  and  sometimes  it  will  go  as  high  as  50, 
but  this  really  makes  no  difference  in  the  paint,  and  in 
view  of  the  fact  that  it  is  a  natural  product  and  may 
from  time  to  time  contain  a  little  gang  rock  some  leeway 
must  be  given  as  regards  its  composition. 

VANDYKE  BROWN 

Vandyke  brown  is  a  native  earth,  and  is  identical 
with  cassel  brown.  It  is  popularly  supposed  that 
Vandyke  first  used  this  pigment  as  a  glazing  color  in 
place  of  bitumen,  and  as  it  is  composed  of  clay,  iron  oxid, 
decomposed  wood,  and  some  bituminous  products,  it  is 
fairly  translucent  and  adapts  itself  for  glazing  purposes. 
Because  of  the  bitumen  which  it  contains,  it  dries  very 
badly  and  very  slowly,  and  has  a  tendency  to  crack  or 
wrinkle  if  the  under-coat  is  either  too  hard  or  too  soft. 
Concerning  its  permanence,  there  can  be  no  doubt  that 
it  darkens  considerably  on  exposure,  like  all  the  bitumi- 
nous compounds,  and  many  painters  use  a  permanent 
glaze  composed  of  a  mixture  of  ochre  and  black  tinted 


77 

with  umber.     Where  the  effect  of  age  is  to  be  simulated, 
there  is  no  objection  to  its  use.1 

This  pigment  is  used  in  mixed  paints,  principally  on 
account  of  its  deep  shade  and  translucent  appearance. 
It  contains  upwards  of  60  per  cent  of  organic  matter. 
A  typical  analysis  would  be  as  follows: 

Organic  Matter 65  % 

Ferric  Oxid 3  % 

Calcium  Carbonate 5  % 

Potash  and  Ammonia  Salts 2  % 

Moisture 25  % 


'Materials  for  Permanent  Painting"  by  Maximilian  Toch. 


CHAPTER  VI 

THE  YELLOW  PIGMENTS 

THE  yellow  pigments  are  the  ochres,  the  raw  siennas, 
chrome  yellow,  and  the  chromates. 

The  ochres  are  all  rust-stained  clay,  and  both  the 
French  and  the  American  contain  approximately  20  per 
cent  of  rust  or  ferric  hydroxid  and  the  balance  clay. 

The  raw  siennas  differ  from  the  ochres  in  that  the 
amount  of  hydrated  oxid  of  iron  is  often  in  excess  of 
that  of  clay,  and  the  nature  of  the  pigment  is  such  that 
when  finely  ground  it  is  a  stain  and  not  a  paint. 

The  chrome  yellows  are  all  lead  chromate  variously 
precipitated  and  of  varying  composition,  depending  upon 
the  shade. 

The  other  chromates,  such  as  zinc  chromate  and 
barium  chromate,  have  come  into  use  in  paints  within 
the  last  ten  years,  owing  to  their  alleged  property  of 
preventing  rusting. 

AMERICAN  YELLOW  OCHRE 

There  are  large  quantities  of  ochre  found  in  the 
United  States,  but  principally  in  Pennsylvania  and  in 
Georgia.  There  are,  of  course,  a  great  many  other 
deposits,  but  for  the  paint  industry  these  are  the  prin- 
cipal sources.  American  ochre  ranges  in  composition 
from  10  to  30  per  cent  of  ferric  hydroxid,  the  balance  in 
either  case  being  clay,  and  on  this  point  it  is  well  to  note 
that  ochre  and  sienna  have  the  same  composition,  except- 
ing that  there  is  generally  a  reversal  in  the  percentages 

78 


THE   YELLOW  PIGMENTS 


79 


of  clay  and  oxid  of  iron.  Some  ochres  found  in  America 
are  finer  than  those  imported  from  France,  although 
French  ochres  as  a  general  rule  are  decidedly  more 
brilliant  in  color. 

In  the  trade  there  are  many  other  ochres,  which  are 
sold  under  the  name  of  cream  ochre,  gray  ochre,  white 
ochre,  and  golden  ochre,  all  of  which  are  clays  containing 
either  carbonaceous  matter 
or  iron  rust,  for,  after  all, 
ochre  is  simply  clay  stained 
with  rust. 

Cream  ochre  contains 
as  low  as  5  per  cent  of 
iron  rust  or  ferric  hydroxid, 
the  balance  being  silica 
and  clay.  It  has  very  little 
hiding  power,  and  is  con- 
sidered of  very  little  value 
as  a  primer  on  wood,  for 
which  it  is  used  to  quite 
a  large  extent. 

Gray  ochre  is  silica, 
clay,  and  carbonaceous  coloring  matter,  or  is  colored 
with  a  trace  of  ferrous  hydroxid  or  greenish  rust.  It  is 
used  as  a  filler,  or  for  a  cheap  paint. 

White  ochre  is  nothing  more  or  less  than  clay,  and 
has  no  value  whatever  as  a  paint  material. 

Golden  ochre  is  either  French  ochre  or  American 
ochre  which  is  brightened  with  some  chrome  yellow. 
There  are  various  shades  of  golden  ochre  sold,  depending 
upon  the  shade  of  chrome  yellow  with  which  it  is  mixed. 
Some  of  them  are  perfectly  orange  colored,  and  contain 
as  high  as  12  to  15  per  cent  of  chemically  pure  orange 
chrome  yellow. 


No.  22.  ORDINARY  AMERICAN  WASHED 
OCHRE  —  Photomicrograph  X250,  pow- 
dered and  bolted;  lower  in  iron  than 
the  French,  but  of  uniform  grain. 


8o 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


Green  ochre  is  similar  in  composition  to  gray  ochre, 
excepting  that  it  contains  a  larger  percentage  of  ferrous 
hydroxid.  It  is  principally  found  in  Bohemia  under 
the  name  of  terre  verte.  It  has  little  or  no  hiding  power 
of  itself,  but  is  very  largely  used  as  a  base  for  cheap 

lakes  on  account  of  its 
adsorbent  quality  for  cer- 
tain aniline  colors. 

Yellow  oxid  is  a  syn- 
for  raw  sienna,  and 

Practically     the     same 
A  typical  analysis 
yellow   oxid  will  show 
hydrated  oxid  of  iron  70 
per  cent  and  clay  30  per 
cent. 

For  the  benefit  of  the 
chemist  it  must  be  stated 
that  when  analyses  are 
not  given  and  small  percentages  of  lime  and  magnesia 
are  found,  it  is  understood  that  these  are  natural  con- 
comitants of  ochrey  earths. 

FRENCH  YELLOW  OCHRE 

French  yellow  ochre  has  been  used  in  America  for 
many  years,  and  is  analogous  in  composition  to  American 
ochre;  but  as  a  general  rule  the  French  ochres  are  more 
brilliant  in  shade.  Nearly  all  of  the  French  ochres  which 
are  imported  into  the  United  States  have  a  composition 
of  about  20  per  cent  of  hydrated  oxid  of  iron  and  80  per 
cent  of  clay,  and  one  of  the  most  popular  brands  has 
for  years  been  known  as  J.  F.  L.  S.  These  letters  stand 
for  "Jaune,  Fonce,  Lave,  Surfin,"  which  mean,  "Yellow, 
Dark,  Washed,  Superfine."  These  letters  are  varied 


No.  23.  AMERICAN  WASHED  OCHRE  — 
Photomicrograph  X250,  of  the  same 
composition  as  French  ochre. 


THE   YELLOW  PIGMENTS 


8l 


according  to  the  treatment  that  the  ochre  gets,  but  the 
J.  F.  L.  S.  is  the  most  popular. 

In  color,  the  French  ochres  are  more  brilliant,  as  has 
been  stated,  but  the  American  ochres  are  invariably 
finer;  but  this,  of  course,  refers  only  to  the  American 
grades  of  equal  price. 

CHROME  YELLOW 

Chrome  yellow  is  a  lead  chromate  of  medium  shade, 
as  precipitated  from  a  solution  of  nitrate  of  lead  and 
potassium  bichromate.  The 
lemon  or  lighter  shades  are 
made  from  solutions  acidi- 
fied with  organic  or  inor- 
ganic acids.  An  organic 
acid  such  as  citric  acid, 
which  forms  a  lead  citrate, 
changes  the  shade,  pro- 
ducing a  greenish  lemon, 
which  may  vary  from  a 
greenish  lemon  to  a  bril- 
liant canary,  particularly  NO.  24.  J.  F.  L.  s.  OCHRE  —  Photo- 

if    Sulphuric   be   added.       If         ™crograph  X25o,  showing  crystalline 

structure. 

an  alkaline  solution  of  po- 
tassium   bichromate    be    used    an    orange    precipitate   is 
produced,  so  that  a  great  variety  of  shades  of  this  pigment 
can  be  obtained. 

All  of  the  chrome  yellows  are  perfectly  permanent, 
provided  they  are  thoroughly  washed  to  free  them  from 
residual  salts.  Manufacturers  are  now  abandoning  the 
old  mechanical  method  of  stirring  chrome  yellow  after 
it  is  precipitated,  and  are  substituting  air  stirring,  which 
avoids  any  possible  tendency  to  produce  lead  sulphide, 
the  air  converting  the  sulphide  into  sulphite  and  sulphate. 


82  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

Chrome  yellows  when  thoroughly  washed  are  permanent 
to  light,  but  they  cannot  be  recommended  where  sulphur 
vapor  is  generated,  owing  to  the  formation  of  lead  sul- 
phide, traces  of  which  detract  from  the  brilliancy  of  the 
color  of  the  pigment. 

The  composition  of  chrome  yellow  is  as  follows: 

LIGHT  CHROME  YELLOW 

PbSO4  +  PbCrO4 

or, 
2PbCO3  •  Pb(OH)2  +  PbCrO4 

or, 
PbCrO4  +  Citrate 

Tartrate        [  of  Lead 
or  Sulphate  J 

MEDIUM  CHROME  YELLOW 

PbCrO4 

ORANGE  CHROME  YELLOW 
PbO  •  PbCr04  =  Pb2Cr05 

CHROMATE  OF  ZINC 

Chromate  of  zinc  has  only  come  into  general  use 
within  the  last  ten  years  in  mixed  paints  and  paints 
generally,  on  account  of  its  alleged  rust  preventing  prop- 
erties when  used  as  a  priming  paint  on  steel. 

Chromate  of  zinc  is  made  as  follows:  Zinc  oxid  is 
boiled  in  a  solution  of  potassium  bichromate  for  several 
hours  and  filtered  and  dried  with  slight  washing;  or  a 
hot  neutral  solution  of  zinc  sulphate  is  precipitated  with 
potassium  chromate. 

Chromate  of  zinc  is  soluble  to  a  considerable  extent 
in  water,  and  therefore  should  not  be  used  as  a  finishing 
coat,  as  rain  will  streak  the  surface.  For  example,  a 
green  paint  made  of  chromate  of  zinc  and  blue  shows 
yellow  streaks  when  exposed  to  the  weather. 


THE    YELLOW  PIGMENTS  83 

This  material  is  used  to  some  extent  by  artistic 
painters,  and  as  oil  paintings  are  never  subjected  to  the 
elements  it  is  under  those  circumstances  a  perfectly  per- 
manent color. 

For  interior  painting  and  flat  wall  paints,  chromate  of 
zinc,  therefore,  has  an  advantage,  as  much  more  brilliant 
tones  are  obtained  and  much  more  delicate  shades  are 
obtained  than  with  the  chromate  of  lead.  It  has  very 
little  hiding  power  or  opacity,  and  in  tinctorial  strength 
is  much  weaker  than  the  chromate  of  lead. 

If  contained  in  a  mixed  paint,  when  the  pigment  is 
thoroughly  washed  with  benzine  and  freed  from  oil  or 
medium,  chromate  of  zinc  can  easily  be  recognized,  be- 
cause the  pigment  when  shaken  with  hot  water  in  a  test 
tube  is  invariably  colored  yellow.  This,  however,  must 
be  further  verified,  as  barium  chromate  reacts  the  same 
way. 


CHAPTER  VII 

THE  BLUE  PIGMENTS 

THE  blue  pigments  usually  used  in  the  paint  industry 
are  artificial  ultramarine  blue,  artificial  cobalt  blue,  and 
Prussian  blue.  The  types  of  Prussian  blue  vary  very 
greatly  with  their  manufacture,  and  are  known  under 
the  names  of  Milori  blue,  Bronze  blue,  Chinese  blue, 
Antwerp  blue,  Paris  blue,  etc. 

Ultramarine  and  cobalt  blues  are  permanent  to  light 
and  alkali-proof.  The  Prussian  blues  are  permanent  to 
light,  but  not  alkali-proof. 

ULTRAMARINE  BLUE1 

Ultramarine  blue,  whether  it  is  artificial  or  genuine,  is 
chemically  the  same,  with  the  one  difference  that  the 
genuine  ultramarine  blue  is  the  powdered  mineral  known 
as  lapis  lazuli,  and  ordinarily  is  the  blue  known  under 
that  name.  Furthermore,  the  mineral  itself  is  found  at 
times  in  an  impure  state  either  admixed  with  slate  or 
gang  rock,  or  contaminated  slightly  with  other  minerals, 
and  the  genuine  ultramarine  blue  may  run,  therefore, 
from  a  very  deep  blue  to  a  very  pale  ashen  blue;  in  fact, 
the  lapis  lazuli  which  lies  adjacent  to  the  gang  rock  is 
ground  up  and  sold  under  the  name  of  ultramarine 
ashes,  which  is  nothing  more  nor  less  than  a  very  weak 
variety  of  genuine  ultramarine  blue. 

From  the  standpoint  of  exposure  to  light  or  drying 
quality,  the  artificial  ultramarine  blue  is  just  as  good 

1  "Materials  for  Permanent  Painting,"  by  Maximilian  Toch. 

84 


THE  BLUE  PIGMENTS 


as  the  genuine,  and  the  only  advantage  that  the  genuine 
has  over  the  artificial  is  that  the  genuine  is  not  so  quickly 
affected  by  acids  as  the  artificial  is. 

It  may  be  of  interest  to  know  that  in  1814  Tessaert 
observed  the  accidental 
production  in  a  soda  oven 
at  St.  Gobain  (France)  of 
a  blue  substance  which 
Vanquelin  declared  to  be 
identical  with  lapis  lazuli. 
In  the  following  year  the 
same  observation  was 
made  by  Huhlmann  (at 
St.  Gobain  in  a  sulphate 
oven)  and  by  Hermann 


No.    25.   ULTRAMARINE    BLUE  • 
micrograph  xjoo. 


Photo- 


in     the     soda     works     at 

Schoenebeck  (Prussia). 

In  1824   La   Societe  d'Encouragement  pour  Industrie 

offered  a  prize  of  6000  francs  for  the  production  of  artificial 

ultramarine  blue,  \Vhich, 
in  1828,  was  awarded  to 
J.  B.  Guinet,  a  pharmacist 
of  Toulouse,  later  of  Lyons, 
who  asserted  that  he  first 
produced  ultramarine  in 
1826.  Vanquelin  was  one 
of  the  three  "trustees," 
holding  the  secret  contrary 
to  the  rule  of  the  Societe. 
In  December,  1828, 
Gmelin  of  Goettingen  ex- 
plained his  process  of  mak- 
ing artificial  ultramarine 

before  the  Acadamie  des  Sciences  of  Paris.     He  used  as 


No.  26.  ULTRAMARINE  BLUE,  ground  in 
oil,  very  uniform  and  fine  —  Photo- 
micrograph X25O. 


86  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

the  basis  a  mixture  of  precipitated  hydrate  of  alumina 
and  silex,  which  was  later  on  superseded  by  China  clay 
(kaolin). 

In  1829  Koettig  produced  ultramarine  at  the  Royal 
Saxon  porcelain  factory  at  Meissen. 

In  1834  Leverkus,  at  Wermelskirchen,  and  later  at 
Leverkusen,  on  the  Rhine,  produced  the  pigment. 

In  1837  Leykauf  &  Zeltner,  at  Nueremberg,  introduced 
the  manufacture  of  ultramarine  into  Germany. 

Prices  of  ultramarine  in  1830: 

Natural $50.25  per  pound 

Artificial 4.05  per  pound 

Ultramarine  is  composed  of  alumina,  silica,  soda,  and 
sulphur,  as  follows: 

Ultramarine  (pure  blue)  containing  a  minimum  of 
silica  seems  to  be  a  more  or  less  well-defined  chemical 
body,  i.e.,  a  double  silicate  of  sodium  and  aluminium 
with  sulphur  as  a  poly-sulphide  of  sodium,  or  as  a  thio- 
sulphate. 

Ultramarines  Poor          Rich 

in  Silica  in  Silica 

Alumina 29.00  23.70 

Silica 38.50  40.80 

Soda 22.50  19.30 

Sulphur 8. 20  13.60 

Undecomposed 1.80  2.60 


100.00    100.00 


R.  Hoffman  gives  the  following  proportions: 

Alumina      Silica 

Poor  in  silica 100  128 

Rich  in  silica 100  170 


THE  BLUE  PIGMENTS  87 

In  resistance  to  alum  the  different  products  rank  as 
follows : 

Lapis  Lazuli First 

Artif .  Ultramarine  (rich  in  silica) ....     Second 
Artif.  Ultramarine  (poor  in  silica)  . .  .       Third 

In  1859  Leykauf  discovered  the  purple  and  red  varie- 
ties of  ultramarine,  which  were  produced  by  the  action 
of  hydrochloric  and  nitric  acids,  and  by  heating  ultra- 
marine with  calcium  chloride,  magnesium  chloride,  and 
various  other  chemicals.  In  this  way  there  were  pro- 
duced a  variety  of  shades,  and  by  the  addition  of  such 
substances  as  silver,  selenium,  and  tellurium,  even  yellow, 
brown,  purple,  and  green  shades  were  produced. 

All  of  these  colored  ultramarines  are  exceedingly 
permanent  to  light,  but  have  little  or  no  hiding  power, 
and  when  used  alone  are  perfectly  permanent. 

The  ultramarine  blue  which  is  made  by  means  of  a 
potash  salt  instead  of  a  soda  salt  has  every  analogy  of 
color  and  shade  to  genuine  cobalt  blue,  excepting  that 
the  genuine  cobalt  blue  is  not  affected  by  acids  as 
rapidly  as  the  artificial. 

ARTIFICIAL  COBALT  BLUE 

The  cobalt  blue  of  commerce  is  the  same  as  ultra- 
marine blue,  the  difference  being  in  the  shade.  Ultra- 
marine, when  mixed  with  thirty  parts  of  a  white  pigment, 
such  as  zinc  oxid,  produces  a  violet  shade,  whereas  the 
cobalt  blues  when  mixed  in  the  same  proportion  produce 
a  turquoise  or  sky-blue  shade.  Chemically,  the  com- 
position of  these  ultramarines  and  cobalts  will  average 
about  50  per  cent  silica,  22  per  cent  alumina,  15  per  cent 
sodium  sulphide,  in  combination  with  3  per  cent  water 
and  10  per  cent  sulphur.  The  addition  of  the  slightest 


CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 


trace  of  acid  to  a  paint  containing  ultramarine  blue 
liberates  H2S,  which  always  indicates  the  presence  of 
ultramarine  in  a  blue  or  bluish  pigment.  Under  the 
microscope  ultramarine  blue  has  a  distinct  crystal- 
line appearance.  When  these  crystals  are  badly  de- 
stroyed by  fine  grinding  the  color  suffers  very  much,  the 
characteristic  brilliant  blue  of  ultramarine  becoming  an 
exceedingly  muddy  shade.  Its  tinctorial  power  is  very 
weak,  but  it  is  exceptionally  permanent  to  light.  In 

blue  shades  of  mixed  paints 
the  percentage  of  ultra- 
marine blue  can  be  deter- 
mined either  by  difference 
or  by  the  percentage  of 
sulphur  present.  If  10 
per  cent  is  accepted  as 
the  amount  of  sulphur  in 
ultramarine  blue,  a  fairly 
accurate  quantitative  de- 
termination can  be  arrived 

No.  27.  ARTIFICIAL  COBALT  BLUE  (same  at.  Where  ultramarine  blue 
as  ultra  blue)  -  -  Photomicrograph  js  mixed  with  lithopone  the 
X 250,  crystalline  grain.  .  i  r-j  r  ^.i.  IVT. 

zinc  sulphide  of  the  litho- 

pone  as  well  as  the  ultramarine  evolve  H2S.  When  deter- 
mining the  ultramarine,  the  total  H2S  evolved  must  be 
calculated  as  sulphur.  The  zinc  must  be  precipitated  as 
carbonate  and  weighed  as  oxid  and  calculated  to  sulphide. 
The  sulphur  in  the  ZnS  must  then  be  deducted  from 
the  total  sulphur.  From  the  difference  the  percentage 
of  ultramarine  blue  in  the  original  pigment  may  be  cal- 
culated. As  acetic  acid  liberates  the  H2S  from  the 
ultramarine  but  does  not  attack  the  S  in  lithopone,  this 
acid  may  be  used  and  the  percentage  of  sulphur  in  the 
ultramarine  determined  directly. 


THE  BLUE  PIGMENTS  89 

Ultramarine  blue  reacts  with  corroded  white  lead 
but  not  with  zinc  oxid.  It  does  not  react  very  quickly 
with  sublimed  lead  or  zinc  lead,  but  for  the  making  of 
pale  blue  shades,  which  should  remain  permanent  in  the 
package,  zinc  oxid  is  to  be  recommended  in  preference 
to  any  other  white  pigment.  Ultramarine  blue  should 
not  be  mixed  with  any  of  the  chrome  yellows  or  chrome 
greens,  because  a  darkening  effect  is  sure  to  take  place. 
Ultramarine  blue  behaves  very  badly  with  linseed  oil 
containing  an  excessive  amount  of  lead  drier.  For  mixed 
paints  of  pale  tints  a  resinate  of  manganese  or  oleate  of 
manganese  drier  is  to  be  recommended.  Most  of  the 
Japan  driers  contain  large  quantities  of  lead,  and  a  white 
Japan  composed  of  rosin,  manganese  and  linseed  oil  will 
make  the  most  permanent  mixture. 

PRUSSIAN  BLUE 

Synonym :  Milori  Blue,  Bronze  Blue,  Antwerp  Blue,  Chinese  Blue, 

Paris  Blue,  etc. 

Almost  every  text-book  on  elementary  chemistry 
gives  a  description  of  Prussian  blue,  which  is  a  ferri-ferro- 
cyanide  of  iron,  and  in  a  general  way  it  can  be  produced 
for  laboratory  purposes  by  the  simple  mixture  of  ferro- 
cyanide  of  potassium  and  a  ferric  salt  of  iron.  Com- 
mercially, the  well-known  ferric  iron  reaction  of  analytical 
chemistry  is  reproduced  on  a  large  scale.  Prussian  blue, 
however,  is  made  from  a  ferrous  salt  and  is  obtained  by 
the  mixture  of  ferrous  sulphate  (copperas)  and  ferro- 
cyanide  of  soda  or  potash  (yellow  prussiate).  This  mixture 
produces  a  pale  bluish  white  flocculent  precipitate,  and  the 
chemist  will  easily  understand  how,  with  the  addition  of 
any  oxidizing  agent,  such  as  bleaching  powder,  potassium 
chlorate,  etc.,  the  precipitate  is  converted-  from  a  bluish 
white  into  a  dark-blue  pigment. 


90  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

There  are  a  number  of  varieties  of  Prussian  blue,  all 
approximating  this  composition  but  made  differently, 
being  sold  under  the  names  of  Steel  blue,  Milori  blue, 
Bronze  blue,  Antwerp  blue,  Chinese  blue,  and  Paris  blue. 
Although  each  of  these  blues  is  chemically  the  same  as 
Prussian  blue,  they  have  different  physical  character- 
istics. Prussian  blue,  for  instance,  is  like  a  mixture  of 
indigo  and  black  in  its  dry  state,  and  when  tinted  with 
one  hundred  times  its  own  weight  of  zinc  oxid  the  shade 
produced  is  a  muddy  violet.  Chinese  blue,  when  treated 
in  the  same  manner,  gives  a  purer  blue  which  has  no 
trace  of  violet  in  the  shade.  The  Steel  blue,  when  diluted 
one  hundred  times,  gives  a  turquoise  shade.  And  so  for 
the  manufacturer  of  pale  blue  shades  the  tones  of  these 
blues  must  be  taken  into  consideration. 

There  is  much  discussion  among  paint  manufacturers 
as  to  whether  Prussian  blue  is  a  permanent  pigment  or 
not,  and  the  author  is  frank  to  say  that  this  matter  can 
be  decided  as  follows :  Prussian  blue,  or  any  of  its  varieties 
may  be  considered  permanent  or  fugitive,  according  to  the 
manner  in  which  it  is  made  and  according  to  the  base 
with  which  it  is  mixed.  If  Prussian  blue  contains  more 
than  a  trace  of  soluble  salt  (sodium  sulphate),  it  has  a 
decidedly  yellowing  action  on  the  oil,  and  a  light  blue 
or  light  green  made  of  such  Prussian  blue  is  supposed  to 
be  fugitive.  On  the  other  hand,  a  number  of  experi- 
ments made  with  thoroughly  washed  Prussian  blue  have 
demonstrated  that  it  is  a  perfectly  stable  color  and  does 
not  change  its  shade.  As  a  tinting  color  for  making  pale 
blues  in  mixed  paints  Prussian  blue  has  caused  an  enor- 
mous amount  of  trouble.  A  pale  blue  mixed  paint  that 
contains  white  lead  in  any  proportion  changes  color  in 
the  package,  'a  reduction  process  taking  place  which 
converts  it  from  a  ferric  into  a  ferrous  state,  so  that 


THE  BLUE  PIGMENTS  91 

when  a  can  of  light  blue  mixed  paint  made  with  Prussian 
blue  and  white  lead  is  opened  it  is  a  sickly  green  instead 
of  a  blue.  If  such  a  paint  be  applied  to  an  exterior 
surface  it  is  completely  converted  into  its  original  blue 
shade  as  soon  as  it  is  dry.  The  zinc  oxid  paints  have  the 
same  action,  but  to  a  very  small  degree,  and  a  paint 
manufacturer  who  desires  to  make  a  pale  blue  by  the  use 
of  Prussian  or  Chinese  blue  must  avoid  the  use  of  white 
lead  in  his  paint.  The  artificial  cobalt  blue  mixed  with 
zinc  oxid  is,  however,  more  desirable. 

Prussian  blue  is  also  used  in  small  quantities  for  mix- 
ing with  bone  black  to  produce  intensely  black  shades. 

It  is  a  simple  matter  to  determine  the  presence  of 
Prussian  blue  in  any  pigment  by  the  addition  of  caustic 
soda  to  the  dry  extracted  pigment,  warming,  filtering, 
and  testing  the  filtrate  with  a  drop  of  ferric  chloride  after 
acidifying.  The  Prussian  blue  made  in  laboratories 
will  contain  approximately  30  per  cent  of  iron,  so  that  if 
an  analysis  is  made  of  a  mixed  paint  tinted  with  Prussian 
blue  and  the  percentage  of  iron  is  multiplied  by  three,  a 
fairly  correct  estimate  of  the  percentage  of  Prussian  blue 
is  obtained;  and  while  the  factor  given  cannot  be  abso- 
lutely correct,  owing  to  the  difference  in  the  various 
blues  made,  it  is  so  nearly  correct  that  a  synthesis  made 
from  such  an  analysis  has  invariably  given  the  same 
shade. 


CHAPTER  VIII 

THE  GREEN  PIGMENTS 

THE  greens  used  in  the  manufacture  of  paints  are 
the  so-called  chrome  greens,  which  are  mixtures  of  chrome 
yellow  and  Prussian  blue,  the  genuine  chrome  greens  or 
chromium  oxid,  the  aniline  lakes,  zinc  green,  and  the 
verte  antique  or  copper  green. 

CHROME  GREEN 

Chrome  green  is  sold  under  various  proprietary  names, 
and  must  not  be  confounded  with  the  oxid  of  chromium. 
Chrome  green  is  essentially  a  mixture  of  Prussian  blue 
with  chrome  yellow,  but  the  chrome  greens,  unless  chemi- 
cally pure,  are  always  mixtures  of  blue  and  yellow  on  a 
barytes  or  mixed  base. 

A  green  paint  made  entirely  of  Prussian  blue,  chrome 
yellow,  and  an  inert  base,  such  as  silica  or  barytes,  is 
very  easily  analyzed  by  ignoring  the  pigment  and  weigh- 
ing the  base,  calculating  the  pigment  by  difference.  This 
is,  however,  not  a  desirable  method  to  recommend  except 
in  the  hands  of  an  expert  who  knows  that  the  pigment  or 
paint  is  made  on  an  inert  base.  Inasmuch  as  there  is  a 
great  variety  of  shades  of  chrome  green,  ranging  from  a 
yellowish  green  to  a  very  dark  olive,  and  as  the  dark 
shades  may  be  composed  of  either  a  mixture  of  orange, 
chrome  yellow,  and  Prussian  blue,  or  a  light  chrome 
yellow  and  Prussian  blue  and  black,  it  is  not  safe  to 
multiply  the  percentage  of  iron  by  a  factor  to  obtain  the 
percentage  of  Prussian  blue,  because  many  shades  of 

92 


THE  GREEN  PIGMENTS  93 

green  are  produced  with  the  use  of  ochre.  The  iron 
factor  would  therefore  be  misleading.  The  lead  chro- 
mate  can  be  washed  out  with  hot  hydrochloric  acid  and 
will  precipitate  on  cooling.  The  Prussian  blue  may  be 
washed  out  with  a  caustic  alkali  solution,  the  iron  being 
left  behind,  but  it  can  be  reprecipitated  as  Prussian  blue 
with  a  ferric  salt,  the  necessary  amount  of  chrome  yellow 
and  Prussian  blue  originally  used  being  thus  recovered. 
This  method  is  uncertain  only  when  an  olive-yellow  is 
being  analyzed. 

Chrome  green  should  never  be  mixed  with  white  lead 
for  the  pale  shades,  as  it  changes  color  in  the  can  in 
proportion  to  its  content  of  Prussian  blue.  Zinc  lead, 
zinc  oxid,  sublimed  lead,  or  lithopone  should  therefore 
be  used.  If  chrome  green  is  not  well  washed  the  soluble 
salts  are  likely  to  affect  the  linseed  oil.  At  the  seashore 
the  salt  atmosphere  invariably  attacks  chrome  green  and 
bleaches  it,  and  where  an  absolutely  permanent  green  is 
required  chromium  oxid  should  be  used. 

CHROMIUM  OXID 
Chemical  Formula :  Cr203 

This  green  is  one  of  the  oldest  greens  in  existence, 
having  been  used  for  very  many  years,  but  never  having 
been  used  for  mixed  paints  or  by  the  paint  manufacturer, 
excepting  for  artists'  use,  until  within  the  past  six  years. 
While  it  is  expensive  compared  to  the  chrome  green  as 
previously  described,  and  while  it  is  weaker  in  tinting 
power  and  lacks  in  brilliancy,  it  nevertheless  is  the  only 
perfectly  permanent  green  made.  It  mixes  with  every 
other  pigment  without  decomposition  and  stands  the 
light  without  fading  or  darkening.  No  alkali  discolors 
it,  and  therefore  in  the  modern  flat  wall  paints  where 
delicate  greens  are  desired  chromium  oxid  has  come  to 


94  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

play  a  very  significant  role.  Many  manufacturers  get 
more  for  their  fancy  colors,  such  as  greens,  blues,  and  ver- 
milions, and  any  man  who  makes  a  perfectly  alkali-proof 
wall  paint  is  entitled  to  a  higher  price  if  the  goods  are 
better  than  those  of  his  competitor. 

Chromium  oxid  frequently  possesses  coarse  qualities. 
It  is  made  as  follows : l 

Eight  parts  potassium  dichromate  and  3  parts  of  pure 
boric  acid  are  ground  with  water  to  a  stiff  paste.  The 
mixture  is  then  heated  to  dull  redness  for  about  4  hours 
in  a  reverberatory  furnace.  The  melt  is  thrown  into 
water  and  boiled,  to  decompose  borates  of  chromium  and 
potassium  into  boric  acid  and  chromium  oxid  (hydrated). 
The  latter  is  then  washed,  dried,  and  ground. 

After  it  comes  out  of  the  dry  room  it  has  to  be  ground 
in  a  burr  stone  mill  with,  water  exactly  like  an  oil  color. 
This  develops  whatever  brilliancy  there  is  in  the  color 
and  increases  its  hiding  power,  but  unfortunately  it  also 
develops  a  "float"  of  a  very  much  more  brilliant  green 
than  the  natural  chromium  oxid.  This  float  is  similar 
in  color  to  the  well-known  Veronese  green  or  hydrated 
oxid  of  chromium,  but  is  not  apparent  in  the  quicker 
drying  types  of  paints. 

Chromium  oxid  is  now  largely  used  as  a  basic  color 
in  automobile  painting,  particularly  in  the  painting  of 
the  hoods,  and  also  for  the  manufacture  of  the  best 
type  of  dark  green  engine  enamels,  because  excessive 
heating,  or  alternate  heating  and  cooling,  does  not  affect 
it  in  shade  as  it  does  the  chrome  green  made  from  yellow 
and  blue. 

There  is  every  reason  to  believe  that  this  pigment 
will  be  used  in  greater  quantities  than  it  has  been  because 
of  its  sterling  qualities. 

1  Chem.  Ztg.  9,  851. 


THE  GREEN  PIGMENTS  95 

GREEN  ANILINE  LAKES 

Flat  wall  paints,  which  are  very  largely  used  in 
America,  are  the  cause  of  the  manufacture  of  certain 
green  aniline  lakes  which  are  not  permanent  to  strong 
light  but  are  permanent  to  alkali,  and  are  therefore  used 
to  some  extent  for  making  very  brilliant  green  house 
paints  for  interior  decoration. 

These  lakes  can  be  readily  tested  by  mixing  them 
with  soapy  water  and  lime,  and  if  they  remain  un- 
changed for  five  minutes  they  may  be  regarded  as 
permanent,  because  the  majority  of  the  aniline  lakes 
which  are  not  alkali-proof  are  immediately  converted 
into  a  yellow  or  yellowish  brown  color  when  mixed 
with  this  reagent. 

The  aniline  lakes  have  no  hiding  power,  but  have 
tinting  strength,  and  are  only  used  as  tints.  For  making 
very  brilliant  greens  that  have  hiding  power  the  chromium 
oxid  is  used  as  a  base  and  the  aniline  colors  to  obtain 
brilliancy. 

ZINC  GREEN 

Zinc  greens  are  generally  mixtures  of  chromate  of  zinc 
and  Prussian  blue,  and  are  extremely  brilliant,  perma- 
nent to  light,  but  not  permanent  to  alkali  or  to  water, 
as  the  chromate  of  zinc  remains  slightly  soluble  under 
many  conditions. 

This  particular  type  of  green  is  also  largely  used  for 
interior  decorative  purposes  and  for  the  manufacture  of 
flat  wall  paints.  It  is  much  more  expensive  than  the 
chromate  of  lead  green.  It  is  also  used  to  some  extent 
as  a  coach  color.  Where  it  is  varnished  over  this  color 
is  not  soluble. 


g6  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

VERTE  ANTIQUE  (COPPER  GREEN) 

The  pigment  for  making  verte  antique  or  antique 
green  for  copper  imitation  is  generally  the  bicarbonate  of 
copper.  It  has  little  or  no  hiding  power,  but  the  corroded 
copper  effect  cannot  be  very  well  imitated  with  any  other 
pigment.  It  is  manufactured  as  follows: 

A  solution  of  blue  vitriol  is  precipitated  with  sodium 
carbonate,  yielding  a  basic  copper  carbonate,  carbon 
dioxid  being  evolved  in  the  course  of  the  reaction. 

2CuSO4+  2Na2CO3+  H2O  =  CuCO3-Cu(OH)2+  2Na2S04  +  C02 

There  are  a  number  of  other  methods  in  use  for 
making  copper  green  which  are  more  lengthy  and  trouble- 
some to  carry  out. 

The  lack  of  hiding  power  of  this  color  is  one  of  its 
good  qualities,  because  the  under  coat  usually  is  a  copper 
color,  made  by  so  mixing  a  para  toner  and  Princess  Metal- 
lic brown  that  the  translucency  of  the  bicarbonate  of 
copper  gives  the  effect  of  actually  corroded  copper. 
Frequently  this  color  is  stippled  on,  and  sometimes  it  it 
flowed  on.  Where  opacity  or  hiding  power  is  wanted 
chromium  oxid  and  bicarbonate  of  copper  are  mixed. 
This  pigment  is  permanent  to  light,  and  is  at  present 
practically  the  only  pigment  made  or  used  which  con- 
tains copper. 


CHAPTER  IX 

THE  BLACK  PIGMENTS 

THE   principal   dry   pigments   used   in   making   black 
paint  are  as  follows: 


Lampblack 
Carbon  Black 
Graphite 
Charcoal 

Vine  Black 
Coal 
Ivory  Black 
Drop  Black 

Black  Toner 
Benzol  Black 
Acetylene  Black 
Mineral  Black 

There  are  quite  a  large  variety  of  bone  blacks,  begin- 
ning with  ivory  black  and  going  down  to  the  by-product 
of  the  sugar  mills  known  as  "Sugar  House  black."  In 
composition  all  of  the  animal  blacks  are  alike,  in  so  far 
as  they  always  contain  carbon  and  calcium  phosphate. 
The  carbon  varies  between  15  and  23  per  cent,  the 
rest  being  phosphate  of  lime  and  moisture.  Some  of 
the  best  blacks  used  for  mixed  paints  are  made  from 
the  shin-bone  and  skull  of  the  sheep,  it  having  been 
found  that  these  blacks  are  of  the  most  intense  color. 
Occasionally  variable  amounts  of  calcium  carbonate  are 
found  in  these  blacks,  depending  largely  upon  the  length 
of  time  the  bone  was  burned.  For  making  a  very  intense 
and  good  quality  black  which  will  not  settle  when  mixed 
with  varnish,  carefully  selected  bones  or  burnt  ivory 
chips  are  taken,  and  digested  in  hydrochloric  acid,  which 
removes  all  the  lime  salts  and  leaves  the  carbon  as  a 
flocculent  residue.  This  carbon  is  probably  the  highest 
priced  and  most  intense  black  used  by  paint  makers, 

97 


98  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

and  is  frequently  sold  under  the  name  of  black  toner, 
because  it  sometimes  is  used  for  giving  an  intense  tone 
to  an  otherwise  pure  black.  In  the  material  known  'as 
Black  Color  in  Varnish,  it  is  found  that  black  toner 
serves  its  purpose  best,  and  a  black  paint  which  is  com- 
posed of  black  toner  ground  in  linseed  oil  and  reduced 
with  a  very  high  grade  of  coach  varnish  is  worth  from 
$4  to  $6  per  gallon. 


LAMPBLACK 

Lampblack  is  the  condensed  smoke  of  a  carbonaceous 
flame,  and  at  present  is  made  from  a  hydrocarbon  oil 
of  the  type  of  dead  oil,  or  it  may  be  made  from  a  number 
of  distillates  which  on  burning  give  a  condensed  black 
soot.  Lampblack  is  still  made  from  resinous  woods, 
tar  and  pitch  where  the  dead  oil  is  not  obtainable,  and 
while  many  people  are  inclined  to  regard  lampblack  and 
carbon  black  as  the  same,  they  are  not  by  any  means  the 
same  from  the  paint  manufacturer's  standpoint,  for  lamp- 
black is  distinctly  gray  when  compared  with  ivory  black, 
bone  black,  or  carbon  black,  and  as  a  general  rule  lamp- 
black makes  a  bluish  gray  when  tinted  out  with  white, 
one  hundred  parts  to  one,  whereas  bone  black  and  ivory 
black  as  a  rule  make  a  brownish  tint.  This  is  an  empiri- 
cal method  for  differentiating  them. 

The  specific  gravity  of  lampblack  is  generally  less  than 
two,  and  one  pound  of  a  very  pure  lampblack  without 
undue  pressure  will  fill  a  package  which  is  over  200 
cubic  inches  in  size,  and  very  often  over  230  cubic 
inches  or  one  American  gallon. 

Lampblack  is  distinctly  an  American  product,  as  is 
evidenced  by  the  enormous  amount  of  blacks  of  this  type 
which  are  exported;  a  careful  search  of  the  imports  fails 


THE  BLACK  PIGMENTS 


99 


to  show  any  appreciable  amount  which  comes  into  this 
country.1 

Lampblack  as  it  is  made  now  is  exceptionally  pure, 
and  contains  more  than  99  per  cent  of  carbon.  Occasion- 
ally, however,  samples  are  found  which  contain  a  small 
percentage  of  unburned  or  condensed  oil,  which  will 
retard  the  drying  of  lampblack  to  such  an  extent  as  to 
make  it  at  times  unfit  for  use.  Prior  to  1906  there  were 
many  cases  where  lampblack  contained  unsaponifiable 
grease,  and  the  author  de- 
vised a  method  for  remov- 
ing this  with  62°  naphtha, 
changing  the  slow  drying 
lampblack  into  one  which 
dried  definitely;  but  since  i 
that  time,  due  to  improve- 
ments in  the  selection  of 
lampblack  and  the  greater 
care  taken  in  its  manu- 
facture, it  is  very  difficult 
to  find  a  lampblack  which 

contains  less  than  99.5  per     N°'  28'  LAMPBLACK  -  Photomicrograph 

X3oo,  very  uniform. 

cent     carbon    and    which 

does  not  dry  within  a  reasonable  time.  It  must  be  taken 
into  account  that  lampblack  is  always  a  slow  drier. 
Whether  this  is  due  to  the  fact  that  it  prevents  the  blue 
rays  of  light  from  entering  the  oil,  or  whether  it  is  an 
inherent  paralysis,  has  not  been  definitely  decided,  but  one 
thing  is  positive,  that  where  lampblack  contains  unburned 
or  condensed  oil  the  drying  is  in  a  large  measure  paralyzed. 

1  A  most  excellent  historical  treatise  on  lamp  and  carbon  blacks 
will  be  found  in  the  original  communications  of  the  Eighth  Inter- 
national Congress  of  Applied  Chemistry,  Volume  12,  page  13,  by 
Godfrey  L.  Cabot. 


IOO 


CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 


CARBON  BLACK 

Carbon  black  is  in  all  respects  similar  to  lampblack, 
except  that  it  is  intensely  black  in  color,  and  while  it 
shows  no  crystalline  structure  under  the  microscope  it 
condenses  itself  so  hard  on  the  places  from  which  it  is 
scraped  that  it  is  largely  interspersed  with  flakes  of  black 
which  to  all  appearance  are  crystalline  and  are  very 
refractory  in  the  mill.  Its  tinctorial  power  is  very  great, 

one  pound  being  sufficient 
to  tint  one  hundred  pounds 
of  white  lead  to  a  dark 
gray.  Paint  manufacturers 
have,  however,  abandoned 
its  use  as  a  tinctorial  ma- 
terial  for  several  reasons, 
the  principal  ones  being 
that  it  is  likely  to  produce 
a  streaky  color  when  used 
as  a  tint,  owing  to  the  pres- 
ence of  very  small  nodules 

^^  d()  nQt  ghow  undl 

it  is  applied  as  a  paint 
(and  these  streaks  cannot  be  brushed  out).  In  the 
second  place  it  shows  a  peculiar  tendency  to  attach 
itself  to  minute  air  bubbles,  so  that  when  made  into  a 
mixed  paint  of  a  lighter  tint  and  allowed  to  stand  in  the 
package  for  a  considerable  time,  fairly  large  amounts  of 
black  rise  to  the  top  of  the  liquid.  Only  with  the  great- 
est difficulty  can  these  be  remixed  with  the  rest  of  the 
pigment  to  produce  a  uniform  tint. 


No.   29.   CARBON  BLACK  —  Photomicro- 
graph xsoo,  very  uniform. 


THE  BLACK  PIGMENTS 


IOI 


GRAPHITE 

Synonym  :  Black  Lead,  Stove  Polish.     Specific  Gravity :  1.19  to  2.5, 
depending  upon  the  impurities  contained  in  it 

Graphite  is  found  as  a  mineral  almost  all  over  the 
world.  It  is  very  largely  used  as  a  paint  pigment,  and 
it  is  remarkable  that  in  its  natural  state  it  has  all  the 
defects  of  bulkiness  which  red  lead  has  for  weight.  The 
purer  a  paint  pigment  is  as  to  its  content  of  carbon  the 
poorer  is  the  paint  pro- 
duced. If  graphite  be  taken 
with  a  content  of  80  or  90 
per  cent  carbon  and  mixed 
with  linseed  oil,  it  forms  a 
porous,  fluffy  film,  and  the 
particles  of  graphite  coagu- 
late in  the  linseed  oil  and 
produce  a  very  unsatisfac- 
tory covering.  If  graphite 
be  diluted  with  a  heavier 
base  its  weakness  then  be- 
comes its  strength  and  a 
very  good  paint  is  formed. 
Many  of  the  characteristic 
chemical  and  physical  defects  of  red  lead  are  largely 
reduced  and  frequently  eliminated  when  it  is  mixed  in 
proper  proportion  with  graphite,  a  high  grade  of  graphite 
when  finely  ground  with  linseed  oil  acting  as  a  lubricant 
and  sliding  under  the  brush. 

Pure  graphite,  as  is  well  known,  will  cover  from  1000 
to  1600  square  feet  to  the  gallon.  Such  a  paint  film  is 
so  exceedingly  thin  that,  while  it  looks  good  to  the  eye, 
in  a  short  period  decomposition  more  easily  takes  place 
beneath  it  than  beneath  many  poorer  paints.  It  is  there- 


No.  30.  NATURAL  GRAPHITE  —  Photo- 
micrograph X2SO,  containing  about 
40  per  cent  of  silica,  showing  crystals 
of  silica  and  graphite. 


102  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

fore  essential  to  reduce  graphite  with  a  heavier  base,  and 
to  this  end  it  has  been  found  that  a  mixture  of  silica 
and  graphite  produces  very  good  results;  but  even  this 
paint  has  the  objection  of  having  too  much  spreading 
power. 

Misnomers  have  crept  into  the  paint  trade  in  regard 
to  graphite  paints,  such  names  as  green  graphite,  red 
graphite,  brown  graphite,  etc.,  being  in  use,  when  in 
reality  such  graphites  do  not  exist,  excepting  as  far  as 
graphite  has  been  mixed  with  pigments  of  these  colors. 

A  six-year  test  of  a 
linseed  oil  paint  made  with 
a  neutral  ferric  oxid,  con- 
taining  in  its  composition 
75  per  cent  ferric  oxid  and 

2O  Per  cent  silica  mixed 
with  graphite  containing  85 
Per  cent  graphitic  carbon, 
nas  Proved  itself  to  be  as 
good  a  paint  as  can  be 
desired  for  ordinary  pur- 
poses. The  pigment  in  a 

No.  31.    NATURAL  GRAPHITE  —  90  per  .  p        i  •        i  •     i          -n 

cent  carbon,  very  finely  powdered.         Pamt      °f      thlS      kmd      Wl11 

withstand  the  chemical  ac- 
tion of  gases  and  fumes,  but  the  oil  vehicle  is  its  weakest 
part. 

Since  the  electro-chemical  industry  has  been  developed 
at  Niagara  Falls  graphite  has  been  made  artificially  and 
is  sold  under  the  name  of  "Acheson  Graphite."  This 
graphite  is  to  be  commended  as  a  paint  material  on 
account  of  its  uniformity  and  fineness  of  grain,  but  it 
should  not  be  used  alone  as  a  pigment,  for  as  such  it 
possesses  the  physical  defect  of  lightness  just  described. 
A  graphite  paint  containing  more  than  60  per  cent  graph- 


THE  BLACK  PIGMENTS 


103 


ite  does  not  serve  its  purpose  very  well  unless  40  per 
cent  of  heavy  pigment  is  added,  such  as  a  lead  or  a  zinc 
compound.  A  rather  unfortunate  defect  in  the  graphite 
paints  containing  a  large  amount  of  graphite  is  the 
smooth  and  satin-like  condition  of  the  paint  film,  which 
is  poorly  adapted  for  repainting.  It  has  often  been 
noted  that  a  good  slow-drying  linseed  oil  paint  will  curl 
up  when  applied  over  certain  graphite  paints,  because 
it  does  not  adhere  to  the  graphite  film.  On  the  other 
hand,  if  particular  forms  of 
calcium  carbonate,  silica, 
or  ferric  oxid  are  added 
to  graphite  a  surface  is 
presented  which  has  a 
"tooth,"  to  which  succeed- 
ing films  adhere  very  well. 
The  question  of  the  co- 
efficient of  expansion  in 
paints  has  not  been  thor- 
oughly considered ,  and 

many     a     good     paint    will    No.  32.  ARTIFICIAL  GRAPHITE  (Acheson) 

fail  because  it  is  tOO  elastic.          -  Photomicrograph     X25o,     contain- 
.„,       .  .  ing  90  per  cent  of  carbon. 

Engineers  sometimes  pre- 
fer a  paint  which  when  scraped  with  a  knife  blade 
will  curl  up  like  ribbon.  Priming  coats  suffer  very 
much  when  they  are  as  elastic  as  this,  but  the  paint 
chemist  can  overcome  these  defects  by  the  proper  ad- 
mixture of  inert  fillers  and  hard  drying  oils. 

Graphite  is  known  as  a  very  slow  drier,  but  this  is 
true  only  when  too  much  graphite  is  used  in  the  paint. 
There  is  no  reason  why  a  graphite  paint  should  not  be 
made  to  dry  sufficiently  hard  for  repainting  within 
twenty-four  hours. 


104 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


CHARCOAL 

It  is  not  generally  known  that  charcoal  from  the 
willow,  maple,  and  bass  trees  is  largely  used  as  a  pigment 
for  black  paints.  There  are  a  number  of  black  paints 
on  the  market  which  are  composed  of  charcoal,  lampblack, 
litharge,  and  linseed  oil  in  varying  proportions,  and  in 
the  early  history  of  these  paints  it  was  difficult  to  make 
them  so  thin  that  they  would  not  turn  semi-solid  in  the 

package.  It  was  found  that 
as  a  preservative  coating 
on  steel  they  did  remark- 
ably well.  Investigations 
by  the  author  have  shown 
that  this  preservative  ac- 
tion is  incidental  and  is 
due  entirely  to  the  alkali 
contained  in  the  charcoal. 
Some  of  the  charcoal  used 
is  a  by-product  from  paper 
mills  and  contains  as  high 
as  2  per  cent  of  potassium 
carbonate.  In  fact,  the 
carbonate  is  produced  by  the  burning  or  calcining  of  wood, 
most  charcoal  being  more  or  less  alkaline.  In  the  exami- 
nation of  paints  of  this  character  it  was  noticed  that  the 
spectroscope  showed  the  potash  lines,  and  thus  it  became  a 
very  simple  matter  to  determine  by  means  of  the  spectro- 
scope whether  a  paint  was  a  charcoal  paint  or  not.  The 
author  has  demonstrated  on  previous  occasions  that  the 
oxidation  of  metal  cannot  take  place  in  the  presence  of 
certain  alkalies,  and  therefore  these  charcoal  paints  when 
freshly  made  are  excellent  preservatives  for  the  metal.  But, 
inasmuch  as  moisture  is  always  present  in  these  paints, 


No.  33.  ARTIFICIAL  GRAPHITE  (Ache- 
son)  —  Photomicrograph  X25O,  uni- 
form in  grain. 


THE  BLACK  PIGMENTS 


having  been  added  in  the  form  of  water  or  contained  in 
the  raw  materials,  saponification  takes  place  more  or  less 
rapidly,  so  that  the  paints 
are  sometimes  unfit  for 
use  two  months  after  they 
are  made. 

The  charcoal  above  re- 
ferred to,  which  is  the 
by-product  from  the  paper 
mills,  while  not  so  suitable 
for  the  manufacture  of 
mixed  paints,  has,  however, 
been  very  largely  used  in 


the  manufacture  of  oilcloth 
and  coated  leather. 


No.  34.   FINE  CHARCOAL  - 
graph  x6oo. 


Photomicro- 


VINE  BLACK 


In  all  essentials  this 


No.    35.   CHARCOAL    BLACK  —  Photomi- 
crograph    x6oo,     showing 
structure  of  the  wood. 

black  in  water,  filter, 
phthalein. 


pigment  is  the  same  as  the  pow- 
dered charcoals  for  paint 
purposes,  excepting  that 
the  grain  is  smaller  and  the 
black  denser.  It  is  made 
in  Germany  by  charring 
the  grapevine.  If  over- 
charred  it  is  likely  to 
become  too  alkaline.  The 
same  tests  may  be  applied 
to  this  black  which  were 
used  for  all  the  charcoal 
and  wood  pulp  blacks,  the 

hexagonal  simplest  and  most  effec- 
tive test  being  to  boil  the 

and   add  a   few  drops  of  phenol- 


io6 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


COAL 

Powdered  anthracite  and  bituminous  coal  are  likewise 
used  in  black  paints,  but  the  origin  of  their  use  is  due  to 
some  extent  to  poorly  written  paint  specifications.  An 
engineer  will  at  times  prescribe  a  paint  containing  a  cer- 
tain percentage  of  ash,  and  in  order  to  meet  this  require- 
ment a  paint  manufacturer  will  have  to  add  coal  in  order 
to  conform  with  the  requirements,  but  as  sulphur  com- 
pounds such  as  SO2  and  SO3 
always  exist  in  coal  a  paint 
is  produced  which  is  ex- 
ceedingly harmful  to  metal. 

IVORY  BLACK 

Ivory  black  is  still  used 
to  some  extent  for  very 
intense  coach  colors,  and 
there  is  also  a  very  fine 
species  of  carbon  black  on 

No.  36.  VINE  BLACK  (German  make)  —    the    market    known    as    the 

Photomicrograph  X2So,  two  sizes  of  "Extract  of  Ivory  Black," 

which  is  made  by  digesting 

charred  ivory  chips  in  hydrochloric  acid  until  nearly  all 
of  the  calcium  phosphate  is  dissolved.  Such  a  black  has 
intense  staining  power,  and  is  by  far  the  blackest  material 
made.  It  is  very  expensive,  colloidal  in  its  nature,  and 
used  therefore  for  ready  prepared  color-in-varnish  or  high 
grade  black  enamels. 


DROP  BLACK 

Drop  black  is  generally  made  by  calcining  sheep  bones, 
which  are  then  impalpably  ground  in  water,  and  when  in 


THE  BLACK  PIGMENTS 


107 


paste  form  cast  into  small  drops;  hence  its  name,  "Drop 
Black."  These  cone-shaped  drops  were  largely  used 
twenty-five  years  ago,  and  then  were  an  indication  of  a 
good  black,  but  at  present  the  name  "Drop  Black" 
still  clings  to  finely  powdered  bone  black.  So-called 
drop  black  is  generally  composed  of  from  10  to  20  per 
cent  of  carbon  and  from  80  to  90  per  cent  of  cal- 
cium phosphate,  and  is  sold  entirely  for  its  intensity  of 
blackness. 


BLACK  TONER 

Black  toners  may  be  either  the  extract  of  ivory 
black,  the  extract  of  bone  black,  or  certain  forms  of 
carbon  black,  or  carbon 
black  upon  which  nigro- 
sine  has  been  precipitated. 
Another  method  for  mak- 
ing black  toner  is  to 
precipitate  red,  yellow,  and 
blue  aniline  upon  the  ex- 
tract of  ivory  black,  which 
produces  an  intensely 
black  pigment  that  is  "$f  :,.. '*3*y,  <&-. 

fc  .    *»  *  '*.  _  .^L  '    •.  '  .!*•**' 

flocculent  and  remains 
in  suspension  a  long  time. 
The  principal  difficulties 
with  these  coal  tar  blacks, 
however,  are:  first,  they  are  not  really  black  in  the 
sunlight;  and  second,  they  paralyze  the  drying  quality 
of  any  varnish  with  which  they  may  be  mixed.  There 
are  a  number  of  specially  fine  blacks  that  can  be  used  for 
black  toners,  such  as  condensed  carbon  from  benzol  or 
acetylene.  Benzol  black  is  remarkably  fine  and  intensely 


;* v  ^  %^-i  >'j'x  j 


•:m'$*v 
•<*.,;•*•' 


No.  37.  WOOD  PULP  BLACK  —  i'hoto- 
micrograph  X5oo,  very  fine  uniform 
grain. 


io8 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


*;  * 


•*  ^  cTr> 
^ 


>^.*-v^-  * 

^    .^v,; 

rXfl 


y 


v 


black,  and  inasmuch  as  there  may  be  an  overproduction 
of  benzol  in  the  United  States  within  the  next  few 
years  it  is  very  likely  that  benzol  black  will  become  a 
reasonable  article  of  commerce. 

BENZOL  BLACK 

Benzol  black  is  a  carbon 
black  which,  however,  is 
much  better  than  the  car- 
bon black  produced  from 
natural  gas.  It  is  soft, 
contains  no  granular  par- 
ticles, and  remains  in  sus- 
pension for  many  weeks 
in  both  oil  and  varnish. 
It  is,  however,  a  very  poor 
drier,  like  most  of  these 
blacks,  and  therefore  a 

mixture    of    litharge   and   red   lead  oil  is   recommended 

when  they  are  to  be  used. 

ACETYLENE  BLACK 

This  black  is  not  quite 
as  common  as  it  was  some 
years  ago.  It  has  very 
desirable  properties  and 
can  be  used  for  tinting 
purposes  without  showing 
granules  or  streaks,  as  is 
often  the  case  with  car- 
bon black  made  from 
gas.  It  is  flocculent  and  somewhat  colloidal  in  nature. 


-1-  a 

-*2 


No.    38.   DROP       BLACK  —  Photomicro- 
graph X3oo,  not  very  uniform. 


No.    39.   DROP       BLACK  —  Photomicro- 
graph X3oo,  very  finely  powdered. 


THE  BLACK  PIGMENTS  109 

MINERAL  BLACK 

Mineral  black  is  usually  composed  of  heavy  black 
slate,  more  or  less  finely  ground,  and  as  a  paint  pigment  is 
inert.  It  is  often  toned  with  lighter  (in  specific  gravity) 
carbons  and  lampblacks,  but  is  not  largely  used  on 
account  of  its  destructive  action  on  paint  mills.  Where 
iron  paint  mills  are  used  these  mineral  blacks  are  found 
to  be  very  expensive,  because  they  will  dull  the  sharpest 
mill  in  a  few  hours'  run.  As  they  possess  very  little 
tinctorial  power  it  is  more  advantageous  to  use  a  200- 
mesh  silica,  tinted  with  lampblack. 


CHAPTER  X 
THE  INERT  FILLERS  AND  EXTENDERS 

THESE  materials,  which  at  times  have  been  called  the 
"reenforcing  pigments,"  have  their  value  when  used  in 
moderate  proportions,  and  yet  it  is  not  within  the 
province  of  any  paint  chemist  to  say  to  what  extent 
these  materials  can  be  classed  as  adulterants  and  to 
what  extent  they  can  be  classed  as  inert  fillers  or  reen- 
forcing pigments.  In  every  case  where  this  question 
comes  up  common  sense,  judgment,  and  best  practice 
provide  the  answer. 

In  the  manufacture  of  mixed  paints,  with  one  excep- 
tion which  will  be  described  later,  every  mixed  paint 
must  contain  an  inert  filler  or  extender,  or  else  the  paint 
will  not  remain  in  a  ready-to-use  form,  but  will  set  hard 
and  lose  much  of  its  value.  In  white  paints  45  per  cent 
of  zinc,  45  per  cent  of  lead,  and  10  per  cent  of  asbestine 
are  regarded  as  a  standard  formula,  and  60  per  cent  of 
these  pigments  are  usually  mixed  with  40  per  cent  of  oil 
to  produce  the  proper  kind  of  paint.  There  are  many 
instances  where  the  inert  fillers  may  reach  as  high  as  20 
per  cent,  that  is,  to  40  per  cent  of  zinc  and  40  per  cent 
of  lead  or  other  white  pigments,  10  per  cent  of  gypsum 
and  10  per  cent  of  white  mineral  primer  are  added  in 
order  to  give  certain  physical  results;  and  yet  there  are 
any  number  of  instances  where  more  than  half  of  the 
paint  in  question  is  composed  of  an  inert  filler,  and  the 
inert  fillers  under  those  circumstances  cannot  be  regarded 


THE  INERT  FILLERS  AND  EXTENDERS  in 

as  adulterants.  If  we  make  a  ready  mixed  paint  of 
ochre  we  are  taking  a  natural  pigment  which  contains 
So  per  cent  of  clay,  and  no  man  can  say  that  the  clay 
naturally  contained  in  ochre  is  an  adulterant.  In  the 
manufacture  of  a  flat  wall  paint  in  which  lithopone  is 
the  principal  pigment  we  have  a  pigment  which  contains 
70  per  cent  of  artificial  barium  sulphate,  and  yet  no  man 
can  say  that  this  artificial  barium  sulphate  is  an  adul- 
terant. In  the  Battleship  Gray  paint  which  the  author 
devised  for  the  United  States  Navy,  it  was  found  that 
the  45  per  cent  of  zinc  and  45  per  cent  of  lead,  with  the 
addition  of  10  per  cent  of  black  coloring  matter,  which 
was  formerly  used,  gave  very  poor  results,  for  such  a 
paint  was  not  salt-water-proof  nor  resistant  to  abrasion; 
but  since  the  United  States  Navy  has  adopted  the  for- 
mula made  by  the  author  of  45  per  cent  of  zinc  oxid,  45 
per  cent  of  blanc  fixe,  and  10  per  cent  of  graphite  and 
lampblack,  a  far  better  paint  is  produced  which  costs 
the  Navy  very  much  less  money  than  the  old  type  of 
paint.  It  is  therefore  not  within  the  province  of  any  man 
to  say  that  the  addition  of  this  45  per  cent  of  blanc  fixe 
constitutes  an  adulterant.  Judgment,  common  sense,  and 
the  particular  case  involved  must  therefore  decide  the 
difference  between  pigment  and  adulterant.  A  large 
number  of  other  cases  can  be  cited,  but  these  are  suf- 
ficient to  illustrate  the  point. 

The  principal  paint  made  which  contains  no  extender 
and  which  remains  in  suspension  is  the  well-known  white 
enamel  paint  composed  entirely  of  zinc,  in  which  the 
medium  is  either  a  heavy  bodied  oil  or  a  damar  varnish. 
This  paint  needs  no  extender  to  keep  it  in  suspension, 
on  account  of  the  very  slight  chemical  action  that  takes 
place  between  the  acids  in  the  oil  or  varnish  and  the  zinc 
itself. 


H2  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

In  spite  of  all  the  good  qualities  of  white  lead  it  has 
been  impossible  up  to  now  to  manufacture  a  ready  mixed 
paint  composed  entirely  of  white  lead  without  the  help 
of  an  extender  like  asbestine  or  a  slight  saponification 
or  emulsification  by  the  addition  of  about  i  per  cent  of 
water. 

It  is  not  so  difficult  to  decide  what  constitutes  an 
adulteration  if  we  take  the  simple  case  of  ready  mixed 
white  paint  intended  as  a  priming  coat,  which  should 
have  the  maximum  hiding  power  and  physical  qualities. 
If  a  paint  like  that  were  composed  of  50  per  cent  white 
pigment  and  50  per  cent  of  barytes  or  whiting,  it  would 
not  possess  the  physical  qualities  necessary  for  a  good 
priming  paint,  and  therefore  the  addition  of  this  quantity 
of  barytes  would  be  strictly  regarded  as  an  adulterant. 

The  principal  fillers  used  in  the  manufacture  of  paints 
are  as  follows: 

Barytes  Calcium  Sulphate 

Barium  Sulphate,  (Artificial)      Clay 

Barium  Carbonate  Kaolin 

Silica  Asbestine 

Infusorial  Earth  White  Mineral  Primer 

Calcium  Carbonate  Whiting 

Gypsum 

BARYTES  (BARIUM  SULPHATE,  NATURAL) 
Formula,  BaSC^;  Specific  Gravity,  4.5 

Barytes  is  a  white  mineral  having  the  same  chemical 
composition  as  precipitated  barium  sulphate.  In  the 
United  States  Geological  Survey  Reports  for  1904,  the 
following  statement  occurs:  "The  value  of  barytes  as  a 
white  pigment  is  being  recognized  more  and  more  each 
year,  and  although  very  little,  if  any,  is  used  alone  for 
this  purpose,  it  is  used  in  large  quantities  in  combination 


THE  INERT  FILLERS  AND  EXTENDERS 


with  white  lead,  zinc  white,  or  a  combination  of  both  of 
these  white  pigments.  This  addition  is  not  considered 
an  adulteration,  as  was  the  case  a  few  years  ago,  for  it 
is  now  appreciated  that  the  addition  of  barytes  makes  a 
white  pigment  more  permanent,  less  likely  to  be  attacked 
by  acids,  and  freer  from  discoloration  than  when  white 
lead  is  used  alone.  It  is  also  believed  that  barytes 
gives  greater  body  to  the  paint  and  makes  it  more 
resistant  to  the  influences  of  the  weather.  As  is  well 
known,  pure  white  lead 
when  remaining  in  the 
shade  or  in  a  dark  place 
becomes  discolored,  turn- 
ing yellowish,  while  mix- 
tures of  white  lead  and 
zinc  white,  or  white  lead 
and  barytes,  or  white  lead, 
zinc  white,  and  barytes 
retain  their  color  perma- 
nently even  in  dark  places." 
The  amount  of  barytes 

,1  i  i         •.-, 

that    Can  ^  be    mixed    With 

colored  pigments  without 
injuring  them  is  remarkably  large.  There  are  hundreds 
of  brands  of  para-red  paints  made  and  consumed  every 
year  by  the  agricultural  implement  trade  which  contain 
as  high  as  90  per  cent  of  natural  barytes.  When  it  is 
taken  into  consideration  that  these  extremely  diluted 
para-reds  cover  well  and  serve  their  purpose  most  admir- 
ably, the  expert  should  be  very  careful  not  to  condemn 
barytes  when  used  in  large  quantities,  for  this  remarkable 
behavior  is  repeated  with  a  large  number  of  other  pigments. 
No  paint  chemist  will  dispute  the  fact  that  barytes 
adds  wearing  quality  to  paint,  but  inasmuch  as  white 


No.  40.   BARYTES,  irregular,  broken  crys- 
tals— Photomicrograph  xsoo. 


H4  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

lead  has  set  the  standard  for  ease  of  working  it  is  ad- 
mitted that  all  the  other  pigments  and  fillers  are  not  as 
unctuous  as  white  lead.  Therefore  the  house  painter 
will  notice  that  the  so-called  lead  combination,  which 
contains  large  quantities  of  barytes,  does  not  work  as 
freely  under  the  brush  as  white  lead;  nevertheless,  this 
objection  does  not  hold  good  when  the  barytes  is  used 
in  moderate  quantities,  that  is,  not  in  excess  of  one  third 
of  the  total  pigment  of  a  paint.  An  experiment  was 
made  with  a  mixture  of  one  third  carbonate  of  lead,  one 
third  zinc  oxid,  and  one  third  barytes  on  an  exposed  wall 
of  a  high  building  in  New  York  City,  in  1885.  *  Up  to 
1905  this  surface  was  still  in  a  moderately  good  state  of 
preservation,  and  as  a  comparison  a  wall  painted  in  1900 
with  a  pure  Dutch  process  white  lead  showed  that  the 
Dutch  process  white  lead  had  not  stood  as  well  in  five 
years  as  the  combination  mixture  had  stood  for  twenty 
years.  It  is  conceded  that  no  paint  is  supposed  to  last 
twenty  years,  but  as  a  matter  of  record  it  is  interesting 
to  note  that  the  inert  filler  added  so  much  to  the  life  of 
the  paint  which  contained  it.  In  view  of  this  fact,  the 
paint  manufacturer  is  justified  in  recommending  to  his 
customers  the  use  of  inert  fillers  in  his  paint  on  the 
ground  of  increased  longevity. 

One  hundred  pounds  of  barytes  will  yield  two  and 
three-quarters  gallons  of  paint.  Owing  to  its  crystalline 
structure  and  specific  gravity  it  is  a  more  expensive  pig- 
ment to  use  than  many  others  when  sold  by  volume,  and 
a  paint  manufacturer  who  uses  barytes  in  a  mixed  paint 
and  thinks  he  is  the  financial  gainer  thereby  is  very  much 
mistaken,  owing  to  the  small  volume  which  barytes  occu- 
pies in  a  mixed  paint.  It  is  also  interesting  to  note  from 
an  experimental  standpoint  that  if  barytes  be  mixed  with 

1  This  building  was  demolished  in  1908. 


THE  INERT  FILLERS  AND  EXTENDERS  115 

linseed  oil  and  turpentine  in  the  proportion  of  two  pounds 
to  a  gallon  it  will  be  found  that,  on  allowing  these  two 
pounds  to  settle  in  a  glass  jar  where  it  can  be  observed, 
it  occupies  only  4  per  cent  of  the  bulk.  In  spite  of 
much  that  may  be  said  in  favor  of  barytes,  it  is  not 
better  than  some  of  the  forms  of  calcium  carbonate  and 
some  of  the  forms  of  silica.  As  an  inert  extender  silica 
has  advantages  over  barytes;  namely,  that  while  it 
produces  the  same  physical  effects  with  equal  wearing 
quality,  its  cost  is  lower 

and  it  produces  a  surface  ^  ^^    Jr.     Jfr*%. 

for  repainting,  having  what  '  $  ^*^S^*'  «*••!•  V 

is    technically    known    as      ,£0V 
"tooth." 

Barytes  is  made  from 
the  mineral  barite,  and 
the  principal  deposits  in 
the  United  States  which 
are  worked  at  present  are 
in  Missouri,  Tennessee,  and 
Kentucky.  There  are  also 

,  ,T.      .    .  i     No.    41.   BARYTES,    AMERICAN* — Photo- 

deposits   in    Virginia    and  micrograph  X3oo. 

in      Georgia,      and     large 

amounts  are  also  found  west  of  the  Mississippi,  but 
freight  plays  a  very  important  role  in  the  shipping 
of  barytes,  and  furthermore,  only  those  mines  nearest 
the  surface  can  be  worked  at  a  profit.  Barytes  is  not 
found  in  ledges  or  solid  masses,  but  rather  in  isolated 
nodules.  The  pieces  vary  in  size  from  an  onion  to  a 
man's  head,  and  vary  in  weight  from  one  ounce  to 
twenty  or  twenty-five  pounds.  There  are,  of  course, 
larger  isolated  lumps  found,  but  generally  speaking  this 
is  the  manner  in  which  the  material  is  mined.  The 
mining  of  barite,  as  a  general  rule,  is  simply  done  in  an 


Il6  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

open  cut,  and  much  of  the  barytes  found  in  the  United 
States  is  associated  with  a  material  called  "chirt,"  which 
looks  like  barytes  but  can  be  very  easily  distinguished 
on  account  of  its  difference  in  weight.  Chirt  is  a  silicate 
of  magnesia  and  alumina,  and  workmen  very  soon  be- 
come adept  in  separating  chirt  from  barite.  Barite  is 
usually  contaminated  with  iron  or  with  a  sticky  ferru- 
ginous clay,  which  can  be  separated  by  weathering  or 
by  washing.  Some  of  the  deposits  in  Virginia  and 
Kentucky  contain  more  than  i  per  cent  of  lime  and 
fluorine,  which  makes  the  ore  undesirable  for  manu- 
facturing purposes  but  is  not  supposed  to  render  it  value- 
less as  a  paint  base.  To  free  it  from  iron  it  is  bleached 
by  what  is  known  as  the  sulphuric  acid  process,  but  as 
it  is  generally  washed,  lixiviated,  and  floated  after  this 
treatment  it  is  very  seldom  contaminated  with  any 
degree  of  acid. 

BARIUM  SULPHATE  (ARTIFICIAL) 

Synonym:   Blanc  Fixe,  Lake  Base,  Permanent  White; 
Specific  Gravity,   4.1-4.2 

When  a  solution  of  chloride  of  barium  is  mixed  with  a 
solution  of  sulphate  of  soda  a  heavy  white  precipitate  is 
formed  which  is  known  as  artificial  barium  sulphate. 
In  all  of  its  chemical  qualities  it  is  identical  with  the 
barytes  of  nature,  but  in  its  physical  qualities  it  is 
totally  different.  Depending  somewhat  on  the  method 
of  its  manufacture,  the  grain  is  exceedingly  fine. 

Blanc  Fixe  has  for  years  been  used  for  the  surface 
coating  of  paper,  because  when  properly  calendered  it 
gives  a  very  high  polish  and  a  permanent  white  surface. 
Originally  it  was  a  French  product,  the  words  "Blanc 
Fixe"  meaning  " permanent  white."  In  the  early  days 
of  the  paper  industry  various  compounds  of  bismuth  were 


THE  INERT  FILLERS  AND  EXTENDERS  117 

used  for  coating  the  paper.  There  are  still  visiting  cards 
in  existence  which  were  surface-coated  by  means  of  bis- 
muth carbonate  and  bismuth  subnitrate.  These  cards 
were  readily  affected  by  sulphur  gases,  and  when  it 
was  found  that  precipitated  barium  sulphate  produced 
an  equally  high  glaze  and  the  surface  retained  its  pris- 
tine whiteness  the  name  "Blanc  Fixe"  was  universally 
adopted  for  the  new  product. 

In  the  paint  industry  it  was  recognized  that  pre- 
cipitated barium  sulphate 
was  a  valuable  adjunct  in 
the  manufacture  of  paint, 
owing  to  the  fineness  of 
the  grain  and  other  physi- 
cal characteristics  of  the 
material.  It  was  found, 
however,  that  when  it  was 
dried  and  powdered  it  had 
lost  its  extreme  fineness 
and  did  not  mix  readily 

with    oil    paints.       In    1895     No.  42.   BLANC  FIXE  —  Photomicrograph 
Henry  M.   Toch  Succeeded         X3°°-     Precipitated  from  cold,  dilute 
i  .  T^T  T-,.  barium  chloride. 

in     making     Blanc     Fixe, 

which,  when  dry,  was  a  soft,  impalpable  powder  of 
great  value  as  a  base  upon  which  to  precipitate  lakes, 
and,  likewise,  when  used  in  mixed  paints  and  enamels 
imparted  to  them,  under  proper  conditions,  a  vitreous 
surface  which  improved  their  wearing  quality.  To  this 
product  the  name  of  Lake  Base  was  given.  A  great 
many  paint  and  chemical  concerns  have  succeeded  since 
then  in  producing  Lake  Base  of  a  soft  fine  texture,  and 
it  has  become  one  of  the  established  bases  of  the  paint 
trade.  Its  intrinsic  value,  when  properly  made,  is  about 
half  that  of  American  zinc  oxid,  but  a  number  of  writers 


Il8  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

have  erroneously  stated  that  its  body  and  covering 
capacity  were  equal  to  zinc  oxid.  Lake  Base  is  success- 
fully used  up  to  70  per  cent  in  white  pigments,  and  in 
colored  pigments  up  to  95  per  cent.  It  is  amorphous 
under  the  microscope,  and  is  used  to  a  great  extent  to 
increase  the  spreading  of  weaker  or  coarser  colors. 

Since  1906  artificial  barium  sulphate  or  Blanc  Fixe 
has  been  used  by  nearly  every  paint  manufacturer  in  the 
United  States,  for  its  excellent  qualities  have  been  proved 
beyond  a  doubt.  The  value  of  this  material  as  a  reen- 
forcing  pigment  or  filler  in  the  manufacture  of  paints  has 
been  thoroughly  demonstrated  by  the  elaborate  experi- 
ments made  by  the  United  States  Navy,  another  indica- 
tion of  how  futile  it  is  for  any  man  to  say  without  careful 
consideration  what  shall  be  regarded  as  an  adulterant 
and  what  shall  be  regarded  as  a  pure  material.  In  1910 
the  Bureau  of  Construction  and  Repair  of  the  United 
States  Navy  had  come  to  the  conclusion  that  the  Bat- 
tleship Gray,  which  had  been  in  use  since  the  termina- 
tion of  the  Spanish- American  war  —  a  period  of  about 
ten  years  —  did  not  give  good  results.  The  formula  for 
the  Battleship  Gray  as  it  then  existed  was  practically 
45  per  cent  of  wrhite  lead,  45  per  cent  of  zinc  oxid,  and 
10  per  cent  of  lampblack.  From  the  standpoint  of  purity 
this  should  be  regarded  as  a  very  pure  paint,  and  from 
all  precedent  it  should  be  inferred  that  a  paint  of  this 
type  would  be  the  best  that  could  be  made;  but  two 
things  demonstrated  themselves  beyond  peradventure. 
One  was  that  such  a  paint  was  not  hard  enough  to  resist 
abrasion;  furthermore,  salt  water  in  the  form  of  spray 
or  the  water  itself  had  a  decidedly  bad  effect.  When  a 
paint  of  this  type  became  wet  it  absorbed  water,  changed 
its  color,  and  became  very  soft  and  spongy.  The  Navy 
officials  most  interested  in  this  consulted  the  author,  who 


THE  INERT  FILLERS  AND  EXTENDERS  119 

devised  a  paint  which  then  would  probably  have  been 
condemned  by  painters  in  general.  Previous  experience, 
however,  had  taught  that  the  addition  of  large  quantities 
of  artificial  barium  sulphate  or  Lake  Base  to  a  proper 
pigment  improved  the  entire  value  of  the  paint,  to  say 
nothing  of  reducing  its  cost  over  20  per  cent.  As  a  result 
the  formula  decided  upon  by  the  author  was:  45  per 
cent  of  zinc  oxid,  45  per  cent  of  Blanc  Fixe  or  Lake  Base, 
and  10  per  cent  of  graphite  and  lampblack.  The  proper 
oils  and  driers  were  then  added.  A  three  months'  test 
was  made  on  the  machine  repair  ship  "Panther,"  and 
when  this  ship  came  back  from  a  cruise  it  was  found  that 
the  paint  was  sufficiently  hard  so  that  the  anchor  chains 
rubbing  against  the  paint  did  not  abrade  it,  and  that 
the  salt  water,  wherever  it  had  wet  the  paint,  did  not 
produce  any  effect  whatever.  For  upward  of  a  year 
the  Navy  experimented  in  a  small  way  painting  other 
ships,  until  in  1915  as  much  as  several  hundred  thousand 
pounds  of  Blanc  Fixe  had  been  bought  by  the  Navy  for 
the  manufacture  of  Battleship  Gray.  There  may  come 
a  time  when  a  new  paint  superior  to  the  present  one 
will  be  devised,  but  this  much  has  been  absolutely  proved 
—that  a  mixture  of  45  per  cent  of  zinc  and  45  per  cent 
of  Blanc  Fixe  for  sea  water  purposes  is  far  better  than  a 
similar  mixture  made  of  zinc  and  lead  only. 

At  the  time  the  Navy  formula  was  originated  Blanc  Fixe 
was  worth  about  2  cents  per  pound,  which  made  a  con- 
siderable saving  to  the  Navy.  At  the  present  writing, 
owing  to  the  European  war  and  the  fact  that  only  one 
concern  is  at  present  manufacturing  Blanc  Fixe  in  the 
United  States  from  American  materials,  and  that  the  de- 
mand is  great  and  the  supply  small,  the  price  has  risen 
to  over  $85  per  ton.  If  the  price  should  rise  as  high 
as  zinc  oxid  or  lead  itself,  it  is  quite  obvious  that  in  view 


120  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

of  the  purity  of  a  paint  made  of  Blanc  Fixe  the  ques- 
tion of  adulteration  could  not  enter.  It  will  therefore 
be  seen  that  this  question  of  adulterated  pigments  is  all 
relative,  depending  entirely  upon  the  results  obtained  and 
upon  the  cost  of  the  material. 

As  far  as  the  influence  of  salt  water  on  a  paint  made 
of  Blanc  Fixe  is  concerned,  the  writer  had  determined 
long  ago  that  the  action  of  sodium  chloride  (salt)  in  the 
air  or  in  water  is  one  of  the  causes  of  the  chalking  or 

decomposition  of  white 
lead.  It  must  not  be  under- 
stood that  the  author  is 
condemning  white  lead  as 
a  pigment.  This  is  simply 
written  to  show  that  there 
are  instances  when  other 
materials  are  better  for  a 
given  purpose. 

Dry  Blanc  Fixe  is  des- 
tined  to  become  a  very 
useful  paint  material.  In 

No.  43.   BLANC  r  IXE  —  Photomicrograph 

X3oo.    Precipitated  from  hot,  con-    1905   there  were  probably 

centrated    acid    solution    of    barium     not      OVCr      IOO      tons      DCr 
chloride. 

year   used.      In    1915    the 

use  had  risen  to  over  3000  tons  per  year,  because  the 
textile  manufacturers  had  also  found  that  its  use  in 
materials  like  linoleum  and  table  oilcloth  not  only  saved 
in  cost  of  manufacture  over  the  higher  priced  pigments, 
but  produced  more  flexible  and  lasting  materials.  The 
same  can  be  said  of  the  printing  ink  manufacturers,  who 
today  are  as  large  consumers  of  dry  Blanc  Fixe  as  the 
paint  manufacturers. 

As  regards  the  manufacture  of  Blanc  Fixe,  this  has 
also  changed  within  the  last  ten  years.  Formerly  it  was 


THE  INERT  FILLERS  AND  EXTENDERS  121 

known  that  only  a  solution  of  barium  chloride  and  a 
soluble  sulphate  or  sulphuric  acid  were  the  raw  materials 
used  for  making  this  product,  but  today  there  are  other 
methods  which  produce  equally  good  materials,  and  in 
some  instances  better  results  than  the  chloride  method. 
For  instance,  barium  sulphide  solution  is  precipitated 
with  sodium  sulphate,  yielding  a  by-product,  sodium 
sulphide,  which  can  be  sold  at  a  considerable  profit. 
The  Blanc  Fixe  so  made  is  denser  than  that  made  from 
the  chloride.  Blanc  Fixe  is  also  made  from  the  peroxid 
of  barium  and  sulphuric  acid,  but  must  be  neutralized 
and  freed  from  peroxid  of  barium  before  it  is  suitable  for 
paint  purposes.  For  certain  color  purposes  the  material 
is  made  from  concentrated  hot  solutions,  which  produces  a 
crystalline  Blanc  Fixe  valuable  for  very  brilliant  colors, 
particularly  greens  and  reds.  Another  method  used  is 
dissolving  barium  carbonate  in  nitric  acid  and  precipi- 
tating with  sulphate  of  soda,  which  then  produces  a  Blanc 
Fixe  equal  to  the  chloride  product. 

BARIUM  CARBONATE 
Formula,  BaCO3;    Specific  Gravity,  4.2;    Synonym,  Durex  White 

This  material  is  practically  new  as  a  paint  material, 
and  has  only  come  into  use  since  flat  wall  paints  have 
had  such  a  tremendous  success  in  the  United  States; 
and  even  at  that,  not  very  many  manufacturers  in  the 
United  States  use  it,  although  it  probably  is  destined  to 
become  as  useful  an  article  as  Blanc  Fixe. 

Barium  carbonate,  under  the  microscope,  has  a  very 
peculiar  structure.  It  is  not  made  by  mixing  a  solution 
of  barium  chloride  and  sodium  carbonate,  although  that 
would  be  the  normal  way  of  making  it,  but  it  is  made 
from  barium  sulphide  and  sodium  carbonate  in  fairly 


122  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

concentrated  solutions,  so  that  the  sodium  sulphide  be- 
comes a  valuable  by-product,  and  therefore  the  barium 
carbonate  can  be  successfully  marketed  at  a  reasonable 
price. 

In  hiding  power  it  is  between  Blanc  Fixe  and  zinc 
oxid,  but  when  used  in  the  proportion  of  45  per  cent 
barium  carbonate  and  45  per  cent  of  zinc  oxid  or  litho- 
pone  in  a  flat  wall  paint  its  physical  quality  makes  it 
particularly  valuable,  because  the  resulting  paint  with 

the   proper    thinners   pro- 

*-  -"  <»«  ^>>  duces  a  velvet  finish  unap- 

-  \  .«**    • 

rV  "^  ^*  *k  preached  by  anything  else. 
Barium  carbonate  such 
as  is  sold  for  paint  manu- 
facture must  not  be  con- 
founded with  Witherite, 
the  natural  form  of  ba- 
rium carbonate.  This  is 

.  .  .      f  ^-  ~v  •    w         ^QfT 

•  V *.>%*•-£*' *~ -*          not   found  in   the  United 

' •  **»          *\  *  •   I      '     ' 

^•.*^**:r*''j?  States,     but      is      largely 

mined  in  England,  Austria 

No.    44.   BARIUM    CARBONATE  —  Photo-  i    ^  T-IT-J.T.      •*. 

and  Germany.     Witherite 

micrograph  X3oo.  J 

has    absolutely    no    paint 

qualifications,  and  is  not  even  as  good  as  barytes. 
In  composition  Witherite  is  identical  with  the  artificial 
barium  carbonate,  but  under  the  microscope  powdered 
Witherite  is  a  transparent  crystalline  material  similar  in 
appearance  to  table  salt. 

SILICA 
Formula,   SiOz',  Synonym,  Infusorial  Earth,  Silex 

The  introduction  of  silex  in  paint  is  due  to  the 
researches  and  investigations  made  by  David  E.  Breninig, 
M.D.,  who  in  the  early  fifties  had  noted  that  when  white 


THE  INERT  FILLERS  AND  EXTENDERS 


123 


lead  was  mixed  with  barytes  it  stood  exposure  better 
than  pure  white  lead.  Late  in  the  fifties  he  came  across 
some  rock  crystal  quartz, 
and,  on  grinding  and  mix- 
ing it  with  white  lead, 
found  that  it  improved 
the  paint.  The  prepara- 
tion of  silica,  especially  for 
the  paint  trade,  became 
an  established  industry 
between  1865  and  1870. 

The  earlier  process  for 
powdering  quartz  was  the 
simple  and  economical 
method  of  dry  grinding  Na  45'  SlLICA'  OR  SILEX— Photomicro- 

...  graph  X25o,  very  fine  grain. 

by  the  tumbling  process. 

The  quartz  was  simply  crushed  to  a  granulated  state  and 
then  put  into  a  tumbling  barrel  with  pebbles,  which  was 

revolved  until  the  silica 
was  reduced  to  a  compara- 
tively impalpable  powder. 
It  was  found,  however, 
that  this  method  was  not 
satisfactory,  because  it  did 
not  produce  uniform  re- 
«  ^*  -  »  H  suits,  and  the  Silex  Lead 

*A  *~    *  ^""          i  '       C» 

*  N  •:'  ~-  Company,  which  had  been 

formed  for   the   manufac- 
ture of   silica  or  silex  for 
No.  46.  SILICA— Photomicrograph  X25o,    the   paint    trade   prior  to 

finely  powdered  and  air  floated,  uniform      1870,   adopted   the   prOCCSS 
angular  grain.  r  ,          .       '     , 

of  heating  the  quartz  to  a 

visible  red  heat,  plunging  it  into  water,  and  crushing  it  after 
the  sudden  change  of  temperature  had  split  the  silica  into 


124 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


a  finer  state  of  division.  The  silica  was  ground  in 
tubs  under  water  with  stone  bottoms  and  drag  stones, 
and  after  it  had  been  thoroughly  comminuted  it  was 
washed,  floated,  dried,  and  then  bolted  to  a  given  degree 
of  fineness.  There  can  be  no  question  that  the  prepara- 
tion of  silica  in  this  manner  produced  a  material  of  great 
uniformity,  the  value  of  which  in  paint  is  unquestioned. 
In  the  early  part  of  the  seventies  tfye  first  practical  tests 
were  made  on  the  coast  of  Maine.  It  was  found  that 

pure  white  lead  would  not 
stand  exposure  at  the  sea- 
shore for  more  than  a  year. 
At  the  end  of  this  time  it 
resembled  whitewash  and 
presented  a  poor  surface 
for  repainting.  A  mixture 
was  made  at  that  time  of 
one  third  silica,  prepared  by 
heating  and  washing,  one 
third  zinc  oxid,  and  one 
NO.  47.  SILICA— Photomicrograph  X2so,  third  white  lead.  These 

very  fine  grain;   this  material  has  been    materials     Were    ground    tO- 
ground  in  water.  .  ,.  ,       M 

gether    in   pure  linseed  oil 

and  sufficient  drier  added.  At  the  end  of  seven  years 
this  paint  was  still  in  good  condition  and  presented  an 
excellent  surface  for  repainting. 

Silica,  like  many  of  the  inert  materials,  has  the  added 
physical  advantage  of  presenting  what  is  known  as  a 
"tooth,"  which  fits  it  exceedingly  well  for  repainting. 
Silica  is  inert  as  an  extender  or  filler  in  paint,  and  does 
not  combine  with  any  other  pigment  or  vehicle.  The 
detection  of  silica  in  mixed  paints  is  very  easily  accom- 
plished by  means  of  the  microscope  and  Nicoll  Prism,  as 
the  metallic  pigments  do  not  polarize.  In  chemical 


-'"-•4|r '  • 

Kip?, 

•''>JS:?$4J*- 

Xz-,  v 
'l^-^fei 


THE  INERT  FILLERS  AND  EXTENDERS  125 

analysis  we  often  find  i  per  cent  of  silica  in  an  otherwise 
pure  paint.  This  i  per  cent  of  silica  generally  shows 
up  in  large  arrow-head  crystals  scattered  throughout 
the  field  of  the  microscopic  vision,  and  is  due  to 
very  small  particles  of  silica  which  have  been  worn  off 
from  the  grinding  stones  of  the  mill.  The  amount  of 
silica  which  may  be  safely  added  to  many  colored  mixed 
paints  without  detracting  from  their  covering  properties, 
and  which  will  increase  their  wearing  qualities,  is  less 
than  one  third  of  the  total  pigments  used. 

The  composition  of  the  various  silicas  on  the  market 
is  quite  uniform,  and  those  that  are  made  from  clear 
colorless  quartz,  or  faintly  colored  quartz,  are  practically 
free  from  iron.  Silica  made  from  rock  quartz  will  assay 
99.7  SiO2. 

Infusorial  earth  is  almost  pure  silica  and  is  largely 
composed  of  the  skeletons  of  diatoms.  It  is  exceed- 
ingly bulky,  and  is  used  by  some  paint  manufacturers 
to  prevent  the  settling  or  hardening  of  paint  in  cans,  and 
owing  to  its  light  specific  gravity  it  accomplishes  this  very 
well  when  added  in  even  as  small  a  quantity  as  10  per 
cent. 

The  question  comes  up  occasionally  as  to  \vhether 
silica  will  hydrate  wThen  heated  and  thrown  into  wrater. 
This  question  must  forever  be  settled  by  the  fact  that 
analyses  of  silica  treated  in  such  a  manner  show  it  to 
contain  99  per  cent  Si02.  If  any  hydration  took  place 
it  would  be  evident  in  the  quantitative  analysis.  There 
can  be  no  doubt  that  the  silicas  obtained  on  the  market 
which  are  washed  and  treated  are  therefore  pure  Si02. 
The  silicas  made  from  infusorial  earth  contain  a  varying 
percentage  of  moisture,  but  the  balance  is  almost  pure 
silica. 


126 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


INFUSORIAL  EARTH;  KIESELGUHR;  FULLER'S  EARTH 

Infusorial  Earth,  Kieselguhr,  and  Fuller's  Earth  are 
forms  of  silica  which  are  diatomaceous  in  nature.  Di- 
atoms are  the  remains  of  plant  life  —  the  silicious 
skeletons  —  the  organic  matter  having  been  entirely  de- 
composed, leaving  these  skeletons.  The  forms  of  these 
skeletons  are  wonderful,  and  a  number  of  illustrations 
will  show  what  they  are  like.  Some  are  like  beautiful 
^  chased  jewels  or  filigree 

work;  others  are  like  the 
covers  of  boxes  made  of 
lace  work;  and  still  others 
are  spear-shaped,  but  all 
of  them  have  the  quality 
more  or  less  of  absorbing 
dyes.  They  are  not  pure 
silica,  for  some  of  them 
are  largely  composed  of 
silica  and  silicate  of  alu- 
mina or  silicate  of  mag- 
nesia. 

These  materials  are 
used  both  as  bases  for  the  lake  colors  used  in  making 
pigments,  and  for  the  purpose  of  preventing  the  settling 
of  certain  classes  of  mixed  paint,  particularly  the  first 
coats  which  are  not  so  finely  ground.  In  this  respect 
these  materials  are  frequently  substituted  for  asbestine, 
because  they  are  more  or  less  free  from  moisture  or 
water  in  combination.  They  can  be  readily  identified 
under  the  microscope  on  account  of  their  very  peculiar 
and  beautiful  forms. 


No.  48.   INFUSORIAL  EARTH  —  Photomi- 
crograph X25o. 


THE  INERT  FILLERS  AND  EXTENDERS 


127 


CLAY 

Composition,  Silicate  of  Alumina;  Synonym,  Kaolin,  Fuller's  Earth 

Clay  in  small  quantities  is  very  largely  used  by  paint 

manufacturers,    first,   to    prevent    settling    or    hardening 

of  mixed  paints,  and  sec- 
ondly, to  produce  unctu- 

ousness  or  good  brushing 

quality.  Clay  occurs  natu- 
rally in  many  paints  up  to 

as  high  as  80  per  cent,  as 

for  instance,  ochre,  which 

is  80  per  cent  of  clay  and 

20    per    cent    of    coloring 

matter.     The    siennas    all 

contain  clay  up  to  as  high 

as   60    per    cent,    and    as 

clay  is  found  naturally  in 

the    pigments    referred   to 

they  cannot,  of  course,  be  regarded  as  adulterated,  but 

when  large  quantities  of 
clay  are  added  to  other- 
wise good  paints  the  wear- 
ing quality  is  reduced,  and 
therefore  more  than  10  or 
15  per  cent  is  not  advis- 
able. Clay  always  contains 
a  large  percentage  of  water, 
and  the  emulsification  that 
ensues  probably  aids  in  the 
non-hardening  qualities  of 

No.    50.   DIATOMS   --   Photomicrograph   pajnt.      In    paste   paints    of 

X6oo,  frequently  found  in  whiting.  ,  .    J 

the    cheaper  variety,   par- 
ticularly barrel  paints,  clay  becomes  a  necessity,  for  these 


No.  49.  DIATOMS  —  Photomicrograph 
X5oo,  found  in  whiting,  clay,  and 
infusorial  earth. 


\ 


128 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


paints  are  sold   at  a  very  low  price,   and   must  remain 
soft  indefinitely  and  easy  to  mix. 

Kaolin  is  a  type  of  clay  which  is  used  by  the  pottery 
trade;  a  typical  analysis  is  as  follows:1 

SiOo 46.27% 

A1203 - 38-57% 

Fe2O3 1.36% 

CaO..                 ..c 0.34% 

MgO 0.25% 

K20 0.23% 

Na2O 0.37% 

H20 13.61% 

101.00% 

It    has    practically    the    same    physical    value    as    the 
ordinary  clay,  excepting  that  the  pottery  clay  is  usually 

whiter  in  color.     Clay  has 
no  hiding  power  or  opacity. 
Kaolinite,  2Si02  •  A12O3  • 
2H2O,  is  the  principal  con- 
stituent of  kaolin. 

ASBESTINE  AND  ASBESTOS 
Asbestine  and  asbestos 
are  silicates  of  magnesia, 
the  asbestine  having  a 
short  fibre  and  the  asbes- 
tos having  a  long  fibre. 

Asbestos  fibre  is  used 
to  a  small  extent  in  paint,  but  it  is  not  as  good  as 
asbestine,  because  the  fibre  of  asbestos  is  too  long. 
However,  considerable  quantities  of  asbestos  are  used 
for  the  making  of  so-called  "fire-proof"  paints,  and  on 
this  subject  it  is  proper  to  say  that  there  is  no  such 

1  Bull.  351  (U.S.  Geol.  Surv.),  Clays  of  Arkansas,  p.  21. 


No.  51.   CLAY — Photomicrograph 


THE  INERT  FILLERS  AND  EXTENDERS 


129 


No.  52.   CHINA  CLAY — Photomicrograph 


thing    at    the    present    time    as  "fire-proof"    paint.      It 

is  perfectly  possible  to  make  a   fire-resisting   paint,   but 

these    paints    usually    are 

of  the  casein-whiting  type. 

Casein,  lime,  phosphate  of 

soda,   and    whiting,    which 

when     mixed    with    water 

produce  fairly  good  kalso- 

mine,  resist  fire  for  a  little 

while.  A  typical  experiment 

has  always  been  to  take  a 

small  shingle,  paint  half  of 

it  with  a  so-called  "fire- 
proof" paint,  and  ignite 

the  uncoated  part;  the  fire  X300. 

dies   out   when   it  reaches  the  painted  part.      This    can 

be    done    with   a   piece   of   wood   from  TV  to   J    inch  in 

thickness,  but  no  timber  or  board  of   any  size  can  pos- 
_______  sibly  be  rendered  fire-proof 

by  paint  application,  for 
when  such  a  piece  of  wood 

-  «***  *»|  or   timber  is  subJ'ected  to 

SC'rJWar'fii^lV     sufficient  heat,  distillation 

of  the  uncoated  wood  on 
the  inside  takes  place,  gas 
is  generated,  and  the  wood 

pr ' •- .JB,  .  t;^v  «£.  **  •^•.f  bursts  into  flame.  The  only 

'*'«*I»*,,k'^  *,.     '/  'ik./k'        successful  method  of  treat- 
*  ^     '"JJi^  '**''  •'  '"**  *n&  w°°d  to  prevent  it  from 

burning    is   by  impregnat- 

No.  53.   COLLOIDAL  Clay  —  Photomicro-     •  •f^     a1lirn      CPuc     UA, 

I'll-,        WJ.LH      cllU.111       SdlLo       Uy 
graph  X3QO. 

means  of  a  vacuum  pro- 
cess; but  this  is  not  painting,  because  the  crystallizing 
effects  of  the  fire-proofing  material  destroy  or  peel 


130  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

any  subsequent  paint  or  varnish,  so  that  up  to  now 
there  has  been  no  fire-proof  paint  made  which  ren- 
ders wood  structures  fire- 
proof. 

For  the  painting  of 
shingles  where  sparks  may 
possibly  ignite  them,  oil 
paints  containing  boracic 
acid  and  powdered  asbes- 
tos are  used,  as  a  paint 
of  this  type  resists  sparks. 
Asbestos  can  be  very 
readily  identified  under  the 

No.  54.   ABESTINE  —  Photomicrograph      micrOSCOpe    On    aCCOUnt    of 

X3°°-  its  long  fibre. 

The  average  analysis  of  asbestine  is: 

Si02 62% 

MgO 31% 

CaO 3% 

Water  of  Crystallization 4  % 

100  % 

CALCIUM  CARBONATE 

Formula,   CaCOs 

Synonyms:    Whiting,  Paris  White,   Chalk,  Marble  Dust,  Artificial 
Calcium  Carbonate,  Spanish  White,  and  White  Mineral  Primer 

Whiting  and  natural  calcium  carbonate  are  prepared 
from  the  natural  chalk  deposits  of  the  cliffs  in  the  south 
of  England,  and  Paris  White,  Extra  Gilder's  White,  and 
Spanish  White  are  all  different  qualities  of  whiting,  de- 
pending on  the  amount  of  levigation  and  fineness  of  grain. 
The  mode  of  preparation  is  very  simple.  It  consists  in 
grinding  the  cliffstone  in  water,  washing  it,  and  allowing 


THE  INERT  FILLERS  AND  EXTENDERS 


it  to  settle  in  large  vats.     The  cream,  or  that  which  is 

nearest  the  surface,  is  dried  over  steam-pipes,  bolted,  and 

sold  as  Paris  White.     The 

next  layers  are  sold  under 

the  name  of  Extra  Gilder's 

White.,     and     the     bottom 

layer  as  Commercial  White, 

of    which   putty    is    made. 

Whiting  is  a  neutral  calcium 

carbonate,     and    with 

exception  of  the  small  per- 

centage  of  water,  which  is 

very  variable  and   depends 

Upon  how  thoroughly  it  has  No-  SS-  WHITIXG  -  -  Photomicrograph 
been  dried,  it  is  remark-  X3oo,  very  uniform  grain. 

ably  pure  and  fine.  The  material  at  the  bottom  of  the 
tubs  known  as  Commercial  Whiting  is  never  used  in 
the  manufacture  of  mixed  paint,  because  it  is  coarse, 

contains  silica  and  iron, 
and  in  attempting  to  grind 
this  grade  the  mills  are 
ruined. 

There  is  a  great  differ- 
ence of  opinion  as  to  the 
merits  of  whiting  in  paint, 
but  it  will  be  conceded 
by  every  manufacturer 
and  paint  chemist  that 
the  addition  of  calcium 
carbonate  in  some  form 


*•»*$ 

w 


or  other  is  of  great  benefit 


No.  56.   GILDER'S  WHITING — Photomi- 
crograph xsoo. 

to     mixed     paint.     Some 

manufacturers  put  5  per  cent  in  all  the  paint  they  make, 
excepting  that  which  is  made  according  to  specification, 


132 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


for  the  excellent  reason  that  any  acid  which  may  either 
develop  in  the  paint  or  be  a  part  of  the  chemical  com- 
position of  the  paint  is 
slowly  neutralized.  For 
paints  intended  for  the 
protection  of  metal  this 
practice  is  to  be  highly 
recommended.  On  the 
other  hand,  some  writers, 
who,  however,  have  had 
little  or  no  practical  ex- 
perience, condemn  calcium 
carbonate  in  any  form  be- 
cause it  lacks  covering 

No.  57-   CALCIUM  CARBONATE  (artificial)  dt       Qr    Mdi  ^ 

— Photomicrograph  X3oo. 

If  a  paint  were   made   of 

100  per  cent  calcium  carbonate  this  statement  would 
hold  true,  but  where  other  solid  pigments  are  added 
the  argument  against  whiting  fails.  No  particular  evi- 
dence need  be  brought  to 
bear  to  prove  the  durability 
of  whiting,  for  the  reason 
that  all  putty  is  made  of 
whiting  and  oil,  and  there 
are  buildings  and  farm- 
houses in  any  number  still 
existing  where  the  putty, 
after  being  exposed  to  the 
elements  anywhere  from 
twenty-five  to  seventy-five 
years,  is,  if  anything,  better  No-  s8.  TALC  (Soapstone)  -  -  Photo- 

,        -    , ,     '  .    j  micrograph  X25o. 

at  the  end  of  that  period 

than  one  month  after  it  was  applied.     Whiting  has  the 

added  advantage  of  being  bulky,  and  priming  coats  in 


THE  INERT  FILLERS  AND  EXTENDERS  133 

which  it  is  used  present  a  good  surface  for  repainting. 
The  amount  that  can  be  used  as  an  assistant  to  mixed 
paint  is  very  variable,  de- 
pending largely  on  the  pig- 
ments used  or  shade  which 

is  made.  Where  a  paint  /^ff^M^SrS^Ki 
is  to  be  made  for  the  in- 
terior of  a  building  in 
which  acid  fumes  are  gen- 
erated whiting  should,  of 
course,  be  omitted.  But 
there  are  so  many  excel- 

~  -  «•  ^V  fji  —      < 

lent  fillers  that  the  use  of  ^*V     ^L 

a  single  One   is  not  always     No.  59.   BASIC  MAGNESIUM  CARBONATE 
necessary.       Whiting    as    it          7  Photomicrograph  X3oo.    Extremely 
,  T  .  light  and  fluffy. 

is   made    today    is    never 

alkaline,  for  in  the  drying  process  it  is  placed  on  steam- 
pipes  and  the  temperature  is  so  low  that  decomposition 

cannot  take  place. 

x>.  .  1    » .  ' .-  r  The  other  forms  of  cal- 

'       V   1  •*  *  *  ^ 
A\%- .\   /'^Vt,  ./'•'•' 'V'.          cium  carbonate  which  are 

in  use  are  produced  by 
grinding  white  marble  very 
fine,  and,  generally  speak- 
ing, these  varieties  are 
better  for  mixed  paint  pur- 
poses than  the  whiting 
made  from  chalk.  In  the 
first  place,  the  ground 

No.  60.  ALUMINA  HYDRATE,  used  as  a  marble  or  limestone  COn- 
base  for  printing  ink  colors— Photo-  ta{ns  litt}e  or  no  moisture; 
micrograph  xaoo.  •  Ai.  j  i  ,1 

in   the  second  place,  they 

are  ground  exceedingly  fine,  and  being  angular  or  crys- 
talline in    shape  they  form   a  better  surface,  if  anything, 


134  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

for  repainting  than  whiting;  and  third,  where  an  absolute 
chemical  composition  is  wanted  they  produce  more  uni- 
form chemical  compounds.  Whiting  and  white  filler 
compounds  bulk  between  3!  and  4!  gallons  per  hundred 
pounds  of  dry  unit. 

There  is  another  grade  of  calcium  carbonate  which 
occasionally  appears  on  the  market  and  is  a  by-product, 
principally  from  soap  works.  It  has  all  the  physical 
characteristics  of  a  good  article,  but  its  chemical  char- 
acteristics condemn  it  at  once  as  a  paint  material  on 
account  of  the  free  lime  which  it  contains.  It  is  worth- 
less for  the  purpose  of  making  putty  and  useless  as  a 
paint  filler.  When  putty  is  made  of  it,  it  forms  a  lime 
soap  and  gelatinizes  the  contents  of  the  packages. 

WHITE  MINERAL  PRIMER 

This  is  a  white  crystalline  limestone  which  is  found 
chiefly  west  of  the  Mississippi,  and  more  largely  used  by 
western  paint  manufacturers  than  by  eastern,  for  the 
freight  is  against  its  shipment  to  eastern  points. 

In  physical  structure  it  is  similar  to  barytes,  but  of 
much  lighter  gravity  and  greater  bulk.  For  instance, 
100  pounds  of  white  mineral  primer  will  yield  4.6  gallons, 
while  100  pounds  of  barytes  will  yield  i\  gallons.  White 
mineral  primer  has  very  little  opacity  or  hiding  power, 
but  it  has  the  physical  quality  of  "tooth,"  and  when 
mixed  with  zinc  or  sublimed  lead  it  is  superior  to  any 
other  form  of  whiting,  with  perhaps  the  exception  of  the 
artificial  calcium  carbonate.  In  many  respects  it  is  similar 
to  finely  powdered  marble  dust. 

MARBLE  DUST 

Considerable  marble  dust  is  used  in  certain  forms  of 
paint,  marble  dust  being  chiefly  composed  of  calcium 


THE  INERT  FILLERS  AND  EXTENDERS  135 

and  magnesium  carbonate  with  i  or  2  per  cent  of 
ferric  oxid.  It  is  a  brilliant  white,  and  when  passed 
through  a  screen  of  200  mesh  is  similar  to  white  mineral 
primer.  Its  chief  use  is  for  carriage  and  coach  paints 
and  also  as  a  primer  for  wood  generally,  because  it  pre- 
vents peeling  on  account  of  its  structure,  having  the 
same  properties  of  "tooth"  which  are  ascribed  to  silica 
and  white  mineral  primer. 

SPANISH  WHITE 

Spanish  White  is  similar  in  all  respects  to  powdered 
chalk,  Paris  White,  or  whiting,  and  at  the  present  time 
is  a  name  only,  for  there  is  little  or  no  whiting  for  paint 
purposes  that  is  now  imported  from  Spain,  all  of  it  being 
of  the  cliffstone  variety  from  England. 

ARTIFICIAL  CALCIUM  CARBONATE 

This  material  has  already  been  referred  to.  It  has 
very  excellent  properties,  but  usually  has  the  one  great 
defect,  viz.  the  small  percentage  of  free  alkali  both 
of  lime  and  soda  which  it  contains,  and  this  produces 
"livering"  of  paints.  Wherever  it  can  be  obtained  in 
neutral  form  it  is  excellent  when  added  in  small  quan- 
tities to  many  priming  paints. 

GYPSUM 

Formula,  CaSO4  +  2H2O 

As  an  inert  pigment  or  filler  gypsum  is  very  largely 
used  in  the  United  States.  It  is  found  in  twelve  states 
and  in  very  large  quantities  in  Canada.  Its  specific 
gravity  is  2.5  and  its  formula  as  cited  above  is  CaSO4 
plus  2H20.  This  formula  represents  the  gypsum  of 
commerce,  as  sold  to  the  paint  trade,  so  closely  that  the 


i36 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


percentage  of  water  in  several  samples  averaged  over  19, 
whereas  the  theoretical  is  20.2. 


No.  61.  AMERICAN  GYPSUM  —  Photo-  No.  62.  AMERICAN  GYPSUM  —  Photo- 
micrograph X25o,  fairly  uniform  micrograph  xsoo,  transparent  flat 
and  flat  crystals.  crystals. 

There  is  a  great  difference  of  opinion  as  to  the  merits 
of  gypsum  as  a  paint  filler,  for  it  must  be  borne  in  mind 


1,'VY  VTr- ;  •  •<•,  *v 
rv%   «»    j- 


# 


,*.  ^' 

^  .F 


'     ^ 
x* 


«F1 


r  O' 

'  ^  .* 

^^^ 

No.  63.  AMERICAN  TERRA  ALBA  —  Pho-     No.  64.   CALCIUM  SULPHATE  (Gypsum) 
tomicrograph      250,  very  finely  pow-  —  Photomicrograph    X25O    (Ameri- 

dered.  can). 

that  if  it  contains  any  free  lime,   or  if  it  is   not  fully 
hydrated,  the  lime  will  act  injuriously  on  the  paint  and 


THE  INERT  FILLERS  AND  EXTENDERS 


137 


thicken  it  unduly.     The  defect  produced  by  its  incom- 
plete hydration  will  be  to  take  up  moisture  from  other 


No.  65.  FRENCH  TERRA  ALBA.—  Pho-  No.  66.  TERRA  ALBA  (French  Gypsum)  — 
tomicrograph  X250,  composition  Photomicrograph  x6oo,  showing  crys- 
CaSO4  +  2  H2O,  same  as  gypsum.  talline  structure  of  calcium  sulphate. 

materials  in  the  paint   so  that  a   hardening    or   setting 
process  goes  slowly  on. 


No.  67.  CALCIUM  SULPHATE  —  Photo-  No.  68.  PRECIPITATED  CALCIUM  SUL- 
micrograph  xsoo.  Ppted.  from  cold,  PHATE  —  Photomicrograph  X3oo.  Note 
moderately  concentrated  solutions.  the  long-fibred  crystalline  structure. 

Some  of  the  gypsum  sold  in  the  east  is  made  from 
alabaster,   this  being  a  native,   translucent  calcium   sul- 


138  CHEMISTRY     AND   TECHNOLOGY  OF  PAINTS 

phate.  The  Pennsylvania  Railroad  in  its  freight  car 
color  permits  the  use  of  70  per  cent  of  gypsum,  and  as 
good  results  have  been  obtained  by  this  company  in  the 
use  of  calcium  sulphate  as  a  filler  the  condemnation  of 
this  material  is  without  much  foundation.  Due  con- 
sideration must  be  given  to  the  fact  that  thousands  of 
tons  of  Venetian  red  are  consumed  by  the  paint  industry 
every  year,  and  that  the  composition  of  Venetian  red 
will  average  from  15  to  40  per  cent  ferric  oxid,  the 
balance  being  entirely  gypsum.  It  is  nevertheless  true 
that  as  one  part  of  gypsum  is  soluble  in  five  hundred 
parts  of  water,  excessive  rainfall  will  erode  it  in  a  paint, 
particularly  where  the  binder  is  easily  attacked. 

Where  calcium  chloride  is  a  by-product  large  quan- 
tities of  calcium  sulphate  are  artificially  made,  and  many 
paint  manufacturers  prefer  the  artificial  calcium  sul- 
phate to  the  natural.  The  photomicrograph  shows  this 
to  have  a  long-fibred  crystalline  structure,  and  while 
it  has  no  chemical  properties  which  are  different  from 
the  natural  gypsum,  its  purity  and  physical  structure 
make  it  valuable  for  many  mixed  paint  purposes. 


THE  INERT  FILLERS  AND  EXTENDERS 


139 


CALCIUM 

WATER 

PERCENTAGE 

SULPHATE 

OF  GYPSUM 

77-45 

20.14 

94.09 

77-79 

21.39 

97-59 

78.44 

20.76 

99.18 

77.46 

20.46 

99-20 

79-30 

48.84 

97.92 

64.63 

18.75 

98.14 

67.91 

17.72 

83.38 

71.70 

18.68 

85-63 

59-46 

16.59 

90.38 

69.92 

18.85 

76.05 

69.26 

21.50 

88-77 

64.22 

14.00 

90.76 

78.22 

/ 

88.80 

76.02 

19.00 

72.60 

77.76 

20.28 

95.02 

98.04 

76.44 

20.02 

7                  • 

94.84 

78.60 

20.31 

96.46 

98.91 

AUTHORITY 

Conn.  Exper.  Station 
Orton,  Ohio  Survey 
David  T.  Day 
G.  E.  Patrick 
E.  H.  S.  Bailey 
E.  H.  S.  Bailey 
E.  H.  S.  Bailey 
E.  H.  S.  Bailey 
Okarche  Cement  Co. 
E.  H.  S.  Bailey 
Paul  Wilkinson 
U.  S.  Geo.  Survey 
Wilbur  G.  Knight 
Calif.  Exper.  Station 
Calif.  Exper.  Station 
G.  P.  Grimsley 
G.  P.  Grimsley 
Conn.  Exper.  Station 
Conn.  Exper.  Station 
G.  P.  Grimsley 


CHAPTER  XI 
MIXED  PAINTS 

WE  have  seen  from  the  foregoing  chapters  the  ma- 
chinery necessary  for  the  manufacture  of  mixed  paints 
and  the  raw  materials  most  generally  used. 

Of  all  the  shades  of  mixed  paints  made,  the  white 
paints  are  the  weakest  and  perish  the  most  quickly,  and 
the  black  paints,  particularly  those  high  in  carbon  and 
the  ferric  oxids,  are  those  which  last  the  longest.  It  is, 
for  instance,  impossible  to  state  which  of  the  white  paints 
is  the  best,  and  individual  opinions  or  single  instances 
are  not  permissible  for  comparison.  A  test  of  white 
lead  at  the  seashore  will  show  that  white  lead  is  not 
as  good  as  other  white  pigments,  and  at  the  same  time, 
in  a  test  in  the  interior  of  the  country,  or  where  climatic 
changes  are  not  generally  marked,  white  lead  will  show 
up  wonderfully  well.  As  an  instance  of  this,  it  may  be 
cited  that  the  United  States  Light  House  Department 
ordered  their  white  mixed  paint  to  be  composed  of  75 
per  cent  zinc  oxid  and  25  per  cent  white  lead,  for  at  the 
seashore  this  mixture  is  better  than  either  pigment  alone. 

A  series  of  experiments  conducted  by  the  author 
showed  that  white  lead  perishes  through  the  action  of 
carbon  dioxid  in  rain  water.  As  soon  as  a  film  of  oil 
becomes  vulnerable  the  white  lead  becomes  soluble  in 
the  rain  water,  the  so-called  chalking  being  traceable 
to  this  cause.  Zinc  oxid  is  also  attacked  by  carbon 
dioxid,  but  not  nearly  as  quickly  as  white  lead.  Sub- 
limed white  lead  is  attacked  still  less  than  zinc  oxid  and 

140 


MIXED  PAINTS  141 

zinc  lead.  The  western  zincs  and  leaded  zincs,  which 
vary  in  their  proportion  of  lead  sulphate,  are  slightly 
more  permanent  than  zinc  oxid,  but  the  moment  an  inert 
filler  such  as  barium  sulphate,  either  precipitated  or 
natural,  silica  or  magnesium  silicate,  are  added  to  the 
white  lead  and  zinc  oxid  paints,  their  resistance  to  atmos- 
pheric influence  is  largely  increased.  Therefore  these  inert 
materials  are  an  improvement  to  paint,  and  where  no 
specification  is  to  be  followed  they  cannot  be  regarded 
as  adulterants.  The  principal  reason  why  these  inert 
fillers  are  not  added  in  greater  quantities  to  white  paints 
is  due  to  the  fact  that  the  consuming  public  is  not  yet 
sufficiently  educated  to  the  use  of  such  materials. 
Lithopone  has  proved  itself  an  extremely  valuable  pig- 
ment, particularly  for  floor  paints  and  for  marine 
paints  where  shades  other  than  white  are  demanded. 
In  no  sense  can  the  70  per  cent  of  barium  sulphate 
which  is  contained  in  lithopone  be  regarded  as  an  adul- 
terant, because  it  is  a  constituent  of  the  paint  itself. 

The  carbon  and  graphite  paints  have  wonderful 
powers  of  resistance,  provided  they  are  properly  diluted 
with  a  heavier  pigment  so  that  the  film  is  thicker. 
The  average  graphite  paint  will  cover  one  thousand  square 
feet  to  the  gallon,  but  the  film  produced  is  so  thin  that 
when  it  once  starts  to  go,  either  through  the  abrasive 
influence  of  the  solid  contents  of  the  atmosphere  or  the 
decomposing  action  of  water,  the  surface  is  soon  exposed; 
but  when  many  successive  coats  are  applied  to  produce  a 
sufficient  thickness  far  better  results  are  obtained. 

The  ferric  oxid  paints  strike  a  happy  medium,  for 
they  cover  from  four  to  six  hundred  square  feet  to  the 
gallon ;  but  their  color  is  limited  to  three  shades  —  red, 
brown,  and  black.  As  priming  and  second  coats  they 
are,  however,  ideal,  and  as  finishing  coats  where 


142  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

these  shades  are  admissible  they  serve  their  purpose 
exceedingly  well. 

No  single  pigment  is  as  good  as  a  mixture  of  pigments, 
and  the  intelligent  combination  of  the  raw  materials 
always  produces  the  best  results. 

There  is  continued  rivalry  between  the  manufacturers 
of  the  lead  pigments  and  the  manufacturers  of  the  zinc 
pigments,  both  of  whom  claim  superiority  for  their 
particular  pigments.  If  you  read  the  advertisements  in 
any  of  the  weekly  journals  or  in  the  paint  magazines 
you  will  see  after  reading  one  advertisement  that  only 
white  lead  is  the  best  pigment,  and  after  reading  another 
advertisement  that  only  zinc  oxid  is  the  best  pigment; 
but  competent  investigators  who  are  more  or  less  honest 
hesitate  to  say  that  zinc  oxid  is  better  than  lead,  or 
that  white  lead  is  better  than  any  other  pigment.  As  a 
matter  of  fact,  it  is  a  very  difficult  thing  to  decide; 
a  just  decision  would  be  that  they  are  all  excellent. 
White  lead,  of  course,  stands  supreme  for  hiding  power. 
There  is  no  pigment  with  the  exception  of  lithopone  that 
will  show  as  much  opacity  as  a  single  coat  of  white  lead. 
On  the  other  hand,  there  is  no  material  that  has  such 
wonderful  qualifications  for  enamel-making  as  zinc  oxid, 
and,  as  a  matter  of  fact,  the  only  single  pigment  that  can 
be  used  and  is  used  for  certain  purposes  is  zinc  oxid,  all 
the  others  being  unsuited  for  the  manufacture  of  prepared 
paints  on  account  of  their  gravity.  It  has  been  con- 
tended that  white  lead  alone  mixed  with  the  proper  oil 
and  driers  has  stood  for  many  years,  and  this  is  quite 
true;  but  zinc  oxid  alone,  as  a  pigment  at  the  seashore, 
does  not  give  as  good  results  as  white  lead,  because  zinc 
oxid  dries  too  hard;  and  yet,  from  the  large  experiments 
made  by  the  author,  a  mixture  of  the  two  is  unques- 
tionably better  than  any  single  pigment,  although 


MIXED  PAINTS  143 

failures  of  mixtures  are  perhaps  as  frequent  as  failures  of 
single  pigments. 

That  mixed  paints  have  become  a  necessity  is  evi- 
denced by  the  fact  that  considerably  more  than  one 
hundred  million  gallons  have  been  made  in  the  United 
States  since  1907.  The  exact  amount  made  at  the  pres- 
ent time  is  very  difficult  to  determine,  but  it  has  been 
estimated  as  being  over  one  hundred  fifty  million  gallons. 
At  the  same  time,  the  production  of  lead  has  increased, 
and  the  production  of  zinc  pigments  likewise.  Likewise, 
the  production  of  both  the  sublimed  white  lead  and  of 
the  sublimed  zinc  and  lead  of  the  Ozark  type  are  increas- 
ing, and  have  come  to  stay,  so  that  the  criticisms  of  the 
various  pigments  are  more  or  less  a  question  of  com- 
mercial rivalry  rather  than  an  inherent  defect  in  any 
of  the  pigments.  They  all  serve  an  excellent  purpose 
and  all  are  exceedingly  useful. 

Many  manufacturers  of  mixed  paints  guarantee  that 
their  paints  will  stand  five  years  under  ordinary  con- 
ditions in  the  United  States.  This  guaranty  is  prob- 
ably excessive,  for  there  are  many  details  which  on 
their  face  appear  insignificant  and  are  not  taken  into 
account  by  a  manufacturer. 

The  priming  of  wood  has  much  to  do  with  the  life 
of  paint,  and  a  paint  that  contains  much  oil  or  vehicle 
to  which  either  pine  oil  or  benzol  has  been  added, 
so  that  penetration  into  the  wood  can  be  effected,  will 
give  much  better  results  than  very  heavy  paints  con- 
taining only  40  per  cent  of  vehicle  and  60  per  cent  of 
solids.  For  the  priming  of  wood  this  proportion  should 
be  reversed  and  the  paint  should  contain  at  least  60 
per  cent  of  liquids  and  40  per  cent  of  solids,  to  which  for 
raw  new  surfaces  a  penetrative  solvent  like  benzol,  toluol, 
or  pine  oil  should  be  added. 


144  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

On  the  other  hand,  the  oxid  of  iron  paints  such  as 
Princess  Mineral  or  Prince's  Metallic  have  been  known  to 
last  twenty  years  on  wooden  barns  in  the  country  dis- 
tricts; this  is  undoubtedly  due  to  the  fact  that  a  reduced 
oxid  of  iron  of  the  Prince's  Metallic  type  is  not  affected 
by  gases,  nor  does  it  react  on  linoxyn.  As  cottages, 
villas,  and  private  residences  are  never  painted  a  dark 
brown  or  a  deep  red  like  any  one  of  the  ferric  oxic  com- 
binations, it  is  therefore  proper  that  this  discussion  relate 
entirely  to  the  lead  and  zinc  pigments  which  are  most 
largely  used  for  the  purposes  mentioned. 

ANTI-FOULING  AND  SHIP'S  BOTTOM  PAINTS 

Anti-fouling  and  ship's  bottom  paints  are  always 
sold  ready  for  use,  and  there  are  two  distinct  types,— 
the  copper  paints  and  the  mercury  paints. 

There  is  a  continual  difference  of  opinion  among  both 
consumers  and  manufacturers  as  to  whether  the  anti- 
fouling  type  of  paint  should  be  one  that  does  not  dry  and 
be  of  the  exfoliating  type,  which  means  that  it  contains 
lard  or  tallow  and  that  when  the  barnacle  or  seaweed 
attaches  itself  it  drops  off  by  its  own  weight,  or  whether 
the  paint  should  be  of  the  poisonous  type,  so  that  when 
the  barnacle  or  submerged  growth  has  absorbed  a  suf- 
ficient quantity  of  the  poison  it  dies  and  drops  off. 
This  is  a  much  mooted  question,  and  there  is  much  to 
be  said  on  both  sides.  Naval  Constructor  Henry  Wil- 
liams of  the  United  States  Navy  has  probably  done  more 
work  on  this  subject  for  the  American  Navy  than  anyone 
else,  and  his  type  of  paint  which  contains  the  red  oxid 
of  mercury  has  undoubtedly  given  far  better  results  than 
any  other  anti-fouling  paint.  The  composition  of  the 
paint  used  by  the  United  States  Navy  is  as  follows: 


MIXED  PAINTS  145 

U.  S.  N.  ANTI-FOULING  PAINT 
6|  gals.  Shellac  Yarn.       15  Ibs.  Zinc  Oxid 
4      "     Den.  Ale.  5    "  Blanc  Fixe 

2\    "     Pine  Tar  25    "  Indian  Red 

2\    "    Turps.  10    "  Red  Oxid  Mercury 

Yield :  15  gals. 

The  copper  paints  which  are  found  on  the  market  con- 
tain from  10  percent  copper  scale  (copper  oxid  —  Cu2O) 
to  as  high  as  40  per  cent.  As  a  rule,  this  is  added  in  a 
very  fine  powder  to  a  mixture  of  linseed  oil,  pine  tar, 
benzol  or  gas  house  liquor,  and  oxid  of  iron  in  some  form, 
usually  of  the  Prince's  Metallic  type,  is  added  as  a 
pigment  for  hiding  power.  This  is  a  so-called  red  or 
brown  copper  paint.  The  green  anti-fouling  is  generally 
a  copper  soap  manufactured  by  saponifying  either  linseed 
oil,  tallow  or  fish  oil  with  caustic  soda,  and  then  adding 
sulphate  of  copper  to  this  soap,  which  produces  an  oleate 
or  linoleate  of  copper  and  sulphate  of  soda  as  a  by-product. 
The  sulphate  of  soda  is  washed  out,  the  remaining  water 
boiled  off,  and  then  pine  tar  and  linseed  oil  added  to  the 
mixture  together  with  chrome  yellow  and  Prussian  blue 
for  hiding  powrer.  This  yields  a  semi-drying  or  non- 
drying  type  of  green  anti-fouling,  which  in  many  instances 
has  given  excellent  results,  but  which  in  some  tropical 
waters  does  not  show  up  as  well  as  the  oxid  of  copper 
paint.  The  copper  paints  do  not  show  up  as  well  as  the 
mercury  paints. 

There  is  a  third  type  which  is  not  a  paint,  but  which 
is  really  a  soap  that  is  applied  hot.  Oleate  or  linoleate 
of  copper  mixed  with  China  wood  oil  when  melted  and 
applied  to  a  thickness  of  about  iV  to  J  of  an  inch  has 
given  very  good  results,  and  it  is  stated  that  this  type 
of  copper  paint  is  a  happy  medium  and  possesses  both  the 
exfoliating  and  the  poisonous  qualities  so  much  in  demand. 


146  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

CONCRETE  OR  PORTLAND  CEMENT  PAINTS 

Portland  cement  is  an  alkaline  rock-like  substance, 
which  after  it  has  set  liberates  lime.  The  literature  is 
replete  with  statements  that  Portland  cement  floors 
cannot  be  painted,  and  it  was  not  until  1903  that  the 
first  successful  experiments  were  made  for  the  painting 
of  Portland  cement.  Prior  to  that  time  all  sorts  of 
things  were  recommended,  such  as  strong  acids  like 
sulphuric  acid  and  acetic  acid,  but  it  was  soon  found 
that  the  application  of  acids  of  this  type  to  Portland 
cement  destroyed  the  Portland  cement  because  it  dis- 
solved out  the  lime  and  left  the  sand  and  aggregate 
loosely  bound. 

Portland  cement  floors  "dust"  up  under  the  abrasion 
of  the  heel,  and  until  a  successful  method  for  painting 
them  was  found  it  was  impossible  to  use  them  in  an 
uncovered  condition.  In  power  houses  where  delicate 
electrical  machinery  was  placed  the  contact  points  were 
ground  out  by  the  silicious  matter  floating  in  the  air 
through  abrasion  of  concrete  under  the  feet.  The  ac- 
companying photomicrographs  show  the  appearance  of 
a  Portland  cement  floor  highly  magnified,  and  indicate 
in  a  general  way  the  necessity  for  painting  Portland 
cement.  In  warehouses,  storerooms  and  offices  generally, 
concrete  floors  had  to  be  covered  with  linoleum  or  wood 
to  prevent  this  continual  dusting,  which  became  obnoxious. 
The  paints  made  of  drying  oils  were  readily  saponified 
and  gave  unsightly  effects,  and  it  was  not  until  the 
publication  of  a  patent  on  this  subject  (U.  S.  Letters 
Patent  No.  813,841)  that  the  trade  in  general  began  to 
understand  that  a  resin  acid  was  necessary  to  combine 
the  lime  and  not  destroy  it.  Previous  attempts  had 
been  made  depending  upon  the  destruction  of  the  lime, 


MIXED  PAINTS 


147 


but  in  this  patent  it  was  first  shown  that  a  chemical 
reaction  took  place  and  the  lime  instead  of  being  de- 
stroyed was  made  to  serve  a  useful  purpose.  A  resinate 
of  lime  was  formed  when  the  coating  applied  had  a 
sufficient  acid  number. 

The  amount  of  free  lime  in  concrete  is  not  very 
great,  for  in  a  1:3  mixture,  that  is,  a  mixture  containing 
one  part  of  cement  and  three  parts  of  sand,  the  top  sur- 
face varies  in  composition  from  0.87  to  1.6  per  cent  of 
free  lime.  A  large  number 
of  analyses  were  made  by 
the  author,  and  it  became 
obvious  that  an  acid  num- 
ber of  5.0  is  sufficient  to 
more  than  neutralize  the 
amount  of  lime  present, 
and  once  neutralized  dust- 
ing does  not  take  place. 
It  is  well  known  that  con- 
crete of  any  kind  and  of 

any      mixture      is      rapidly      Xo.    69.   Photomicrograph    of    Portland 

disintegrated  by  paraffin 
or  machinery  oils  and  re- 
duced in  time.  If,  how- 
ever, the  cement  filler  or 
neutralizing  liquid  is  composed  of  China  wood  oil  and 
a  hard  resin  like  copal,  the  resulting  calcium  resinate 
becomes  insoluble  in  oil,  so  that  oil  dripping  on  a 
floor  of  this  kind  does  not  disintegrate  the  Portland 
cement.  Oil  collecting  on  an  unpainted  concrete  floor 
will  cause  the  floor  to  become  as  soft  as  cheese  in  time, 
and  then  there  is  no  remedy  for  it  excepting  to  take  up  the 
floor  and  put  down  a  new  one.  There  is  no  record  that 
China  wood  oil  and  copal  had  ever  been  used  on  Portland 


cement  floor  composed  of  2  parts  sand 
and  i  part  cement.  This  floor  is  po- 
rous and  will  disintegrate  rapidly  unless 
properly  treated  with  a  cement  floor 
paint. 


148 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


cement  floors  prior  to  the  application  in  question,  and 
that  this  patent  was  new  and  useful  is  demonstrated  by 
the  fact  that  there  are  practically  at  this  writing  over 
forty  Portland  cement  paints  on  the  market,  all  of  them 
based  on  the  same  theory. 

In  1910  it  was  suggested  that  zinc  sulphate  be  used  to 
overcome  the  pernicious  action  of  the  free  lime  in  Port- 
land cement,  and  for  a  time  this  material  had  quite  a 
vogue,  but  it  has  turned  out  that  no  man  could  tell  how 
much  zinc  sulphate  to  use,  for  no  man  knew  definitely  the 

amount  of  free  lime  in  any 
large  area  of  Portland  ce- 
ment, and  therefore  either 
too  much  or  too  little  was 
used.  If  too  little  was  used 
there  was  still  some  free 
lime  left;  if  too  much  was 
used  sulphate  of  zinc  crys- 
tallized out,  and  when  the 
wall  or  floor  became  wet, 
either  through  rain  or 

No.    70.   Highly    magnified     view    of    a      through   Washing,  the   film 
fine    crack    in    Portland    cement    con-      of  paint   peeled   off. 

Practically  all  the  paints 
for  Portland  cement  that 
are  on  the  market  contain  either  China  wood  oil  or  a 
copal  resin  or  both.  Those  composed  of  both  of  these 
materials  have  given  the  best  satisfaction.  Where  ten 
years  ago  there  was  only  one  of  these  paints  on  the 
market  today  there  are  a  large  number,  and  it  is 
estimated  that  more  than  a  million  gallons  per  year 
at  this  writing  are  used  for  the  surface  protection  of 
Portland  cement. 


struction  —  an  example     of     incipient 
disintegration. 


MIXED  PAINTS  149 

PAINT  CONTAINING  PORTLAND  CEMENT 

There  is  only  one  paint  in  existence  thus  far  that 
contains  a  material  equal  to  Portland  cement,  which 
is  a  tricalcium  silicate  and  dicalcium  aluminate,  and 
which  on  setting  liberates  lime.  This  paint  is  known  as 
"Tockolith,"  and  it  has  been  and  still  is  very  largely 
used  among  engineers  for  the  protection  of  steel  against 
corrosion. 

The  author  cannot  go  into  this  subject  any  more 
deeply  because  this  discovery  is  his  and  he  is  interested 
in  the  manufacture  of  this  material,  and  furthermore, 
this  book  is  not  the  place  to  exploit  a  proprietary  article; 
but  inasmuch  as  this  paint  has  been  regarded  by  many 
engineers  as  at  least  a  step  toward  the  solution  of  the 
question  of  the  protection  of  iron  and  steel,  it  is  fitting 
that  this  brief  mention  of  the  material  should  be  made. 


DAMP-RESISTING  PAINTS 

Paints  of  this  character  are  comparatively  new,  the 
first  one  having  been  manufactured  by  the  author's  firm 
and  put  on  the  market  in  1892.  It  was  made  for  the 
purpose  of  coating  brine  pipes  and  pieces  of  machinery 
which  were  continually  under  water.  The  original  paints 
of  this  character  were  produced  by  melting  a  good  grade 
of  asphaltum  and  adding  a  sufficient  quantity  of  gutta- 
percha  together  with  a  suitable  solvent  and  a  small  per- 
centage of  pigment.  These  paints  served  their  purpose 
very  well  and  were  used  very  largely,  but  no  matter  how 
carefully  compounded  the  gutta-percha  separated  from 
the  asphalt  base  if  the  paints  were  allowed  to  stand  for 
any  length  of  time. 


150  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

Further  experiments  showed  that  cement  mortar 
would  adhere  most  firmly  to  such  a  paint.  The  paint 
could  be  applied  even  to  a  new  brick  wall,  lathing 
and  furring  being  omitted.  It  took  such  a  long  time, 
however,  to  introduce  a  paint  of  this  character  to  the 
building  public  that  the  author's  firm  never  thought  it 
worth  while  to  patent  the  application. 

Damp-resisting  waterproof  paints  are  now  an  adopted 
fixture  in  the  paint  industry,  and  while  bitumen  forms 
the  base  of  paints  of  this  character,  treated  China  wood 
oil,  and  treated  linseed  oil  in  which  glycerine  is  replaced 
with  a  suitable  metallic  base,  should  be  added  when 
making  these  paints.  They  are  used  widely  and  in 
various  ways,  having  served  their  purpose  so  well  that 
engineers  are  beginning  to  adopt  such  paints  as  priming 
coats  for  metallic  structures  wherever  cement  or  cement 
mortar  is  to  be  applied,  so  that  oxidation  by  electrolytic 
action  may  be  prevented. 

ENAMEL  PAINTS 

Enamel  paints  in  former  years  were  pigments  ground 
in  varnish,  which  dried  with  a  high  gloss.  Some  people 
objected  to  this  high  gloss,  and  where  a  good  grade  of 
varnish  was  used  the  film  was  rubbed  with  pumice  stone 
and  water  until  it  produced  an  -egg-shell  finish.  This 
then  led  to  semi-gloss  enamel  paints,  and  finally  we  have 
the  misnomer  of  having  perfectly  flat  enamel  paints 
today,  for  the  very  word  "enamel"  indicates  gloss. 

For  decorative  use  the  principal  enamel  paints  are 
white,  but  it  must  be  said  at  the  outset  of  the  chapter 
that  this  subject  cannot  be  thoroughly  treated  in  this 
book.  It  has  become  so  vast  that  it  would  take  a  book 
of  this  size  alone  to  do  the  subject  justice.  There  are 


MIXED  PAINTS  151 

vast  quantities  of  enamel  paints  made  which  are  colored, 
but  these  are  principally  used  for  machinery  of  all  kinds, 
for  automobiles  and  for  the  so-called  enamelling  of  various 
utensils,  such  as  tool  handles  and  the  like.  There  are 
also  vast  quantities  of  black  enamels  made  for  technical 
purposes,  and  these  are  used  for  the  manufacture  of  oil- 
cloth, patent  leather  and  mechanical  appliances.  Those 
for  oilcloth  and  patent  leather  are  true  oil  enamels; 
those  for  mechanical  appliances  are  principally  made  on 
an  asphalt  base.  This  chapter  will  treat  of  the  subject 
of  enamel  paints  for  decorative  purposes,  which  are 
principally  white  and  mainly  based  on  zinc  oxid  ground 
in  a  varnish  or  varnish  oil. 

Prior  to  the  mixed  paint  era  white  enamel  was  made 
by  taking  zinc  oxid  ground  in  either  poppy  oil  or  a 
bleached  linseed  oil,  and  thinning  it  with  damar  varnish 
as  it  was  needed,  and  the  painter  did  this  himself.  But 
as  ready  for  use  enamels  were  demanded  improve- 
ments wrere  made  on  this  type  of  material.  Today 
the  three  types  of  white  enamels  are: 

First.     The  zinc  oxid  types  ground  in  damar  varnish. 

Second.  The  lithopone  types  ground  in  China  wood 
oil  and  rosin  varnishes. 

Third.     The  zinc  oxid  types  ground  in  stand  oil  only.1 

The  damar  type  first  mentioned  is  simple  to  make,  but 
produces  an  enamel  which  does  not  flow  out,  which  sets 
very  quickly  and  which  sometimes  settles  hard  in  the 
package  and  sometimes  does  not,  depending  entirely  upon 
the  gum  damar  used  for  the  purpose.  There  are  a  great 
many  varieties  of  gum  damar  \vhose  acid  figure  ranges 
from  8.  to  26.,  but  the  acid  of  gum  damar  is  very  weak 
as  compared  to  the  acid  of  the  majority  of  copals,  and 

1   Stand  oil  has  been  described  on  page  176  in  the  chapter  on 
Linseed  Oil. 


152  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

does  not  readily  unite  with  a  base  like  zinc;  therefore 
a  damar  type  enamel  remains  in  suspension  for  several 
years.  For  enamel  purposes  damar  varnish  is  usually  cut 
cold,  that  is  to  say,  six  pounds  are  dissolved  in  a  gallon 
of  solvent  in  an  ordinary  vessel  at  room  temperature; 
the  resulting  varnish  is  always  cloudy,  due  to  occluded 
water  in  the  damar.  To  remove  the  latter  the  cold-cut 
damar  is  placed  in  a  steam-jacketed  kettle  and  heated  to 
about  220°  with  steam  under  pressure.  Steam  at  atmos- 
pheric pressure  has  a  temperature  of  212°  F.,  so  that  at 
least  ten  pounds  pressure  is  necessary  in  a  steam-jacketed 
kettle  to  drive  off  the  moisture  contained  in  damar;  but 
when  this  is  done  the  damar  darkens  unless  the  operation 
is  carried  out  in  an  aluminum  or  silver-plated  kettle. 
Such  solvents  like  cymene,  toluol  and  xylol  are  added 
up  to  5  per  cent  to  damar  varnish  to  overcome  the 
cloudiness  with  fairly  good  results,  but  the  action  is  not 
immediate,  and  the  damar  must  be  tanked  for  a  con- 
siderable time. 

The  second  type,  or  lithopone  and  China  wood  oil- 
rosin  varnishes,  are  very  good  for  household  use,  but  not 
so  good  for  painting  furniture,  unless  the  varnish  is 
made  by  an  expert  varnish  maker  with  a  minimum  amount 
of  rosin  and  the  maximum  amount  of  China  wood  oil, 
otherwise  varnish  of  this  type  becomes  hygroscopic  in 
damp  weather  or  sticky  in  hot  weather.  White  pigments 
other  than  lithopone  are  not  recommended  for  enamels 
of  this  type  because  of  the  high  acid  figure  of  the  varnish. 

The  third  type,  in  which  stand  oil  or  linseed  oil  and 
zinc  oxid  are  used  alone,  is  the  popular  type  of  today, 
but  has  the  disadvantage  of  drying  slowly,  yet  this  type 
of  enamel  will  last  for  many  years,  and  stands  exposure 
even  in  the  American  climate  for  about  eighteen  months. 
It  is  made  as  follows: 


MIXED  PAINTS  153 

Ten  pounds  of  zinc  oxid  are  ground  in  ordinary  raw 
linseed  oil,  and  this  paste  after  having  been  finely  ground 
two  or  three  times  is  mixed  with  one  gallon  of  stand  oil, 
and  then  a  gallon  or  less  of  turpentine  or  a  mixture  of 
turpentine  and  turpentine  substitute  is  added.  When 
made  in  this  manner  it  takes  110°  F.  of  heat  four  or  five 
hours  to  dry  it  so  that  it  is  free  from  tack. 

Another  method  is  to  grind  ten  pounds  of  zinc  oxid  in 
japan  drier,  which  may  be  a  drier  made  of  resinate  of 
manganese  and  lead,  and  then  add  ten  pounds  of  this 
paste  to  one  gallon  of  stand  oil.  This  will  air-dry  in  five 
hours,  and  while  it  gives  good  results  for  interior  pur- 
poses it  is  not  recommended  for  exterior  use. 

A  third  method  of  making  these  enamels  is  to  grind 
the  zinc  oxid  together  with  the  stand  oil  in  a  roller  mill, 
and  then  reduce  with  the  necessary  quantity  of  diluent 
and  drier  and  strain  very  carefully. 

All  enamels  made  along  these  lines  have  a  tendency 
to  turn  yellow  in  the  dark.  Some,  in  fact,  turn  exceed- 
ingly yellow  —  almost  the  color  of  beeswax  —  depending 
upon  the  amount  of  chlorophyll  or  green  coloring  matter 
in  the  original  linseed  oil,  and  no  method  has  yet  been 
devised  whereby  this  can  be  prevented.  Many  experi- 
ments have  been  made  by  the  author  tending  toward 
improving  this  with  partially  good  results,  such  as,  for 
instance,  the  addition  of  an  oxidizing  material  like 
hypochlorite  of  lime  to  the  enamel. 

From  the  foregoing  it  is  clearly  evident  that  enamel 
paints  may  be  nothing  more  or  less  than  pigments  ground 
in  boiled  linseed  oil  without  the  addition  of  any  resin  or 
gum,  and  the  effect  produced  is  that  of  high  gloss  and 
flexibility. 


154  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

FLAT  WALL  PAINTS 

Flat  wall  paints  have  come  into  existence  in  the 
United  States,  and  it  is  estimated  that  hundreds  of  thou- 
sands of  gallons  are  now  made  yearly,  and  that  they 
give  excellent  results.  Most  flat  wall  paints  contain 
lithopone  as  a  pigment,  the  photogenic  quality  of  which 
does  not  play  a  great  role  in  interior  painting.  Many 
of  the  flat  wall  paints  contain  as  high  as  20  per  cent  of 
water  in  the  form  of  an  emulsion,  as  is  the  case  where  the 
water  is  admissible  in  mixed  paints;  for  in  England  the 
flat  wall  paints  which  are  sold  under  a  different  name, 
either  in  paste  form  or  ready  for  use,  are  all  white  paints 
containing  a  small  percentage  of  linseed  oil,  and  are  the 
reverse  practically  of  the  American  type  of  paints.  They 
are  called  washable  in  England  when  they  are  washed 
from  the  bottom  up,  for  when  they  are  washed  from  the 
top  down  and  the  water  streaks  the  wall  there  is  danger 
of  dissolving  some  of  the  paint  and  producing  a  bad  effect ; 
whereas  the  American  types  of  wall  paints,  even  those 
that  contain  20  per  cent  of  water,  withstand  the  action 
of  washing  either  from  the  top  down  or  from  the  bottom 
up.  There  are,  of  course,  many  types  which  contain 
no  water,  the  principal  vehicle  for  this  type  of  paint 
being  a  semi-fossil  damar  mixed  with  linseed  oil  or  more 
generally  a  rosin-China  wood  oil  varnish  containing  over 
50  per  cent  of  solvent. 

Many  of  the  failures  of  the  flat  wall  paints  which 
peel  and  disintegrate  are  due  to  the  sizing  on  which  they 
are  painted.  Glue,  shellac  or  cheap  varnish  sizings  are 
generally  worthless  on  plastered  walls,  while  an  oily  resin 
acid  type  of  filler  gives  results  which  are  permanent., 


MIXED  PAINTS  155 

FLOOR  PAINTS 

Wooden  floors  are  painted  as  a  rule  with  a  varnish 
paint  which  dries  hard  over  night  and  produces  a  wear- 
resisting  waterproof  surface.  In  composition,  paints  for 
wooden  floors  are  analogous  to  paints  for  concrete  floors, 
and  are  composed  of  a  minimum  amount  of  oil  which 
dries  by  oxidation  and  a  maximum  amount  of  hard  resin 
varnish.  The  rosin  varnishes,  particularly  those  of  the 
China  wood  oil  type,  do  not  wear  as  well  as  the  hard 
resin  varnishes. 

The  pigments  used  in  floor  paints  do  not  play  a  great 
role.  Numerous  experiments  made  show,  for  instance, 
that  zinc  oxid  is  not  a  useful  pigment  for  the  reason  that 
the  acid  number  of  a  floor  paint  varnish  is  sufficiently 
high  to  combine  with  the  zinc  and  form  an  unstable  paint 
—  one  which  thickens  up  in  the  container  and  becomes 
unfit  for  use  in  a  few  months.  Therefore  lithopone  is 
found  very  useful,  and  the  inert  pigments  are  preferred 
also  for  this  reason. 

SHINGLE  STAIN  AND  SHINGLE  PAINT 

Shingle  stain  is  not  to  be  confounded  with  shingle 
paint.  A  stain  for  shingles  is  translucent;  a  paint  for 
shingles  is  opaque,  and  the  difference  between  the  two 
is  quite  marked.  One  shows  the  grain  of  the  wood,  and 
the  other  gives  a  painted  effect  and  does  not  show  the 
grain.  There  is  hardly  any  difference  between  shingle 
paint  and  the  average  ordinary  mixed  paint,  with  the 
exception  that  some  manufacturers  add  asbestine  in 
order  to  give  it  some  fire-resisting  quality.  On  this  point 
it  is  well  to  mention  that  shingles  that  are  painted,  par- 
ticularly with  fr  paint  that  has  a  fire-resisting  quality, 


156  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

are  superior  to  those  coated  with  shingle  stain,  even 
though  they  may  not  look  as  artistic,  because  sparks 
flying  from  a  chimney  on  a  roof  that  has  been  stained 
and  has  thoroughly  dried  out  are  very  likely  to  ignite 
the  roof. 

Shingle  stain  is  generally  made  from  the  very  brilliant 
pigments  and  crude  creosote.  These  pigments  are  as  a 
rule  ground  in  linseed  oil,  and  two  pounds  are  generally 
added  to  a  gallon  of  creosote.  Ordinary  creosote  oil  is 
used  for  this  purpose,  probably  because  it  has  some  wood 
preservative  quality.  Other  manufacturers  use  ordinary 
kerosene  and  take  two  pounds  of  the  strongest  colors  in 
oil  that  they  can  get.  Still  other  manufacturers  use 
crude  carbolic  acid  or  crude  cresol  and  kerosene,  but 
in  spite  of  all  these  treatments  shingles  rot  just  the  same. 
It  is  the  soft  pastel  effect  which  a  shingle  stain  gives  that 
commends  it  so  highly;  but  the  same  pastel  effect  is 
produced  with  shingle  paint  after  the  lapse  of  a  year 
or  two,  provided  a  good  paint  is  properly  reduced  with 
about  50  per  cent  of  volatile  solvent. 

On  new  work  shingles  are  generally  dipped.  A  bundle 
is  taken  and  dipped  into  a  barrel  and  allowed  to  soak 
so  that  the  wood  will  absorb  all  that  it  can.  On  old 
work,  of  course,  it  must  be  applied  with  a  brush. 

Asbestine  is  frequently  added  in  the  proportion  of 
one  pound  to  the  gallon  of  shingle  stain  containing  heavy 
colors  to  prevent  them  from  settling.  One  of  the  most 
difficult  shingle  stains  or  shingle  paints  to  produce  is  a 
permanent  red.  For  this  purpose  the  oxids  of  iron 
(Fe203)  are  used,  but  wherever  oxid  of  iron  is  exposed  to 
the  sunlight  in  the  presence  of  linseed  oil  or  other  organic 
oils  it  probably  changes  to  a  ferroso-ferric  condition, 
becomes  considerably  darker  and  is  converted  into  a 
brown.  This  is  less  noticeable  in  a  shingle  stain  than  it 


MIXED  PAINTS  157 

is  in  a  shingle  paint,  because  the  shingle  stain  is  largely 
composed  of  a  volatile  solvent,  and  the  small  amount  of 
binder  has  relatively  a  lesser  action  than  the  binder  in 
the  shingle  paint.  It  has  been  suggested,  and  there  is 
probably  some  value  to  the  suggestion,  that  potassium 
dichromate  to  the  extent  of  one  ounce  to  the  gallon 
should  be  ground  in  crystalline  form  with  the  paint 
in  order  to  prevent  any  reduction.  Hypochlorite  of 
lime  has  also  been  suggested,  and  of  the  two  the 
hypochlorite  would  be  the  better  as  long  as  it  would  last, 
because  it  would  not  wash  out  and  be  likely  to  stain  the 
building.  Dichromate  would  be  very  likely  if  it  ran  over 
the  gutters  or  leaders  to  produce  a  bad  stain. 


CHAPTER  XII 

LINSEED  OIL 

THIS  oil  is  still  the  principal  oil  used  in  the  manu- 
facture of  paints,  and  within  the  last  ten  years  very 
extensive  work  has  been  done  on  the  constants  and 
specifications  for  linseed  oils  generally,  as  will  be  noted 
from  the  reports  of  the  American  Society  for  Testing 
Materials  and  several  other  reports  quoted  by  the  author. 

The  raw  linseed  oil  produced  in  the  United  States 
comes  principally  from  the  northwest.  The  foreign  oils 
come  from  Calcutta,  the  Baltic,  and  the  Argentine 
regions.  There  is  considerable  difference  between  these 
oils,  the  Baltic  being  perhaps  the  best  and  very  highly 
prized  by  varnish  makers. 

The  constants  of  linseed  oil  show  very  wide  variations; 
for  instance,  its  specific  gravity  will  run  from  0.931  to 
0.935.  Its  iodine  value  will  vary  from  160  to  195  or 
more,  while  the  saponification  value  will  run  between 
190  and  196.  The  greatest  differences  are  found  in 
North  American  linseed  oil,  the  figures  being  sometimes 
so  perplexing  that  it  is  difficult  to  reconcile  them  with 
the  standards  of  Baltic  oil.  These  discrepancies  are 
easily  traceable  to  the  natural  impurities  found  in  Ameri- 
can linseed  oil,  as,  for  instance,  oils  from  weeds  growing 
in  the  flax  fields.  American  linseed  oil  is  likewise 
inclined  to  show  the  presence  of  water  to  a  greater 
extent  than  fore'gn  oils,  but  this,  however,  is  a  question 
of  age.  If  raw  linseed  oil  is  allowed  to  settle  until  it 
becomes  perfectly  clear  and  shows  no  sediment  or  tur- 

158 


LINSEED  OIL  159 

bidity  at  o°  C.,  it  cannot  be  said  to  contain  water. 
The  question  here  naturally  arises  as  to  the  use  of  the 
term  "pure."  Calcutta  and  the  Baltic  seed  are  freer 
from  foreign  seeds  than  the  American  product,  and 
although  the  amount  of  foreign  seeds  which  appear  as 
weeds  in  the  field  is  very  small,  their  presence  alters  the 
chemical  and  physical  characteristics  of  the  American 
oil.  Taking  Baltic  as  a  standard,  it  could  be  reasonably 
argued  that  American  linseed  oil  is  adulterated,  yet  no 
man  would  have  a  moral  or  legal  right  to  condemn 
American  linseed  oil  because  it  differed  from  the  Baltic. 
On  the  other  hand  both  climate  and  soil  have  a  well- 
known  influence  on  vegetation;  even  the  percentage 
of  oil  derived  from  a  given  seed  cannot  be  said  to  be 
constant.  It  is  also  stated  that  virgin  soil  produces 
better  seed  than  a  replanted  field  and  this  statement 
appears  reasonable. 

To  how  great  an  extent  the  natural  or  negligible 
admixture  of  the  oil  from  foreign  seeds  to  linseed  oil 
affects  the  wearing  quality  of  the  oil,  it  is  impossible  to 
say,  but  it  must  be  admitted  that  an  oil  containing  up 
to  3  or  4  per  cent  of  the  oil  of  foreign  seeds  or  weeds 
will  not  act  as  well  in  the  kettle  for  varnish  or  boiling 
purposes  as  a  purer  oil.  Taking  these  facts  into  con- 
sideration, a  chemist  must  beware  of  giving  an  opinion 
as  to  the  quality  of  linseed  oil,  and  where  there  is  no 
evidence  either  chemical  or  otherwise  that  the  oil  has 
been  intentionally  diluted  with  other  materials  no 
adverse  opinion  should  be  forthcoming.  If  the  exam- 
ination of  linseed  oil  shows  an  appreciable  percentage 
of  paraffin  oil,  it  can  be  positively  inferred  that  no 
weed  growth  had  anything  to  do  with  this  adulterant 
and  the  mixture  must  be  regarded  as  intentional  or 
accidental. 


160  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

Raw  linseed  oil  is  extracted  from  the  seed  by  the 
old-fashioned  method  of  grinding  the  seed,  heating  it, 
placing  it  between  plates  and  then  pressing  it  until  the 
remaining  cake  contains  the  least  possible  quantity  of 
oil.  The  newer  method  is  a  continuous  process  by  which 
the  seed  is  ground  and  forced  in  screw  fashion  through  a 
tube,  the  oil  oozing  slowly  through  an  opening  in  the 
bottom  of  the  tube  and  the  cake  falling  out  at  the  end 
in  flakes.  When  the  seed  is  fed  in  this  manner  without 
heating,  a  better  quality  of  oil  results.  The  third 
method  consists  in  crushing  the  seed  and  extracting  the 
oil  by  means  of  naphtha.  The  resulting  liquid  is  evapo- 
rated, the  naphtha  recovered  and  the  oil  sold  for  painting 
purposes.  It  appeared,  however,  that  this  process,  while 
very  profitable  for  the  manufacturer,  was  not  profit- 
able for  the  consumer,  and  although  it  made  a  very 
fair  paint  oil,  it  was  found  that  for  the  purpose  of  coating 
leather,  oilcloth,  and  window  shades,  the  oil  had  the 
unfortunate  faculty  of  soaking  through  the  fabric,  and 
when  a  piece  of  goods  was  rolled  up  too  soon  and 
allowed  to  stand  for  the  greater  part  of  the  year  it 
was  almost  impossible  at  the  end  of  that  time  to  unroll 
the  goods,  the  whole  having  become  a  solid  mass.  Inves- 
tigation showed  that  some  of  the  proteids  in  soluble 
form  were  extracted  by  the  naphtha.  This  was  called 
"new  process  oil,"  and  it  was  generally  understood  that 
cake  made  from  new  process  oil  was  not  as  good  cattle 
feed  as  cake  made  in  the  old-fashioned  way,  probably  on 
account  of  the  removal  of  part  of  the  proteids. 

If  linseed  oil  were  uniform,  both  as  to  source  and 
nature  of  seed,  a  chemical  formula  could  be  established 
for  it,  but  because  it  is  not  uniform  the  acids  cannot 
be  given  in  quantitative  relation.  Linseed  oil  should 
give  no  test  for  nitrogen;  if  it  does,  the  proteids  in  the 


LINSEED  OIL  161 

seeds  have  been  attacked.  Probably  95  per  cent  of  all 
the  linseed  oil  made  is  sold  in  the  raw  state,  and,  strange 
to  say,  probably  95  per  cent  or  over  of  all  the  linseed 
oil  used  is  consumed  in  any  other  but  the  raw  state.  It 
must  not  be  inferred  that  all  paint  manufacturers 
manipulate  or  treat  their  linseed  oil  by  heat  and  other 
methods  of  oxidation,  for,  while  many  of  them  claim  to 
do  so,  not  one  that  the  author  is  acquainted  with  could 
afford  to  handle  and  manipulate  linseed  oil.  At  the  same 
time,  raw  linseed  oil  cannot  be  used  for  the  purpose  of 
making  paints  unless  a  drier  be  added,  and  from  the 
very  moment  that  the  drier,  either  in  the  nature  of  a 
siccative  oil,  resin,  or  Japan,  is  mixed  with  the  oil,  the 
chemical  constants  of  the  oil  are  altered.  The  change  is 
an  irreversible  reaction.  As  an  example,  it  may  be  cited 
that  if  90  per  cent  of  linseed  oil  be  mixed  with  10  per 
cent  of  volatile  constituents  and  Japan  driers,  the  chemist 
cannot  separate  the  three  substances  and  produce  three 
vials  containing  raw  linseed  oil  in  the  state  in  which  it  was 
used,  and  the  drier  in  an  unaltered  condition.  The  volatile 
solvent,  if  it  be  benzine,  is  the  only  one  of  the  three  that 
can  be  recovered  in  any  approach  to  its  original  condition. 

The  literature  on  raw  linseed  oil  is  very  incomplete, 
and  more  attention  should  be  paid  by  chemical  experts 
and  writers  to  the  subject  of  identification  of  linseed 
oil  as  it  really  exists  in  the  paint. 

In  the  chapter  on  the  "Analysis  of  Oils"  it  will  be 
seen  that  when  the  iodine  number  of  an  oil  is  180  the 
same  oil  when  extracted  from  mixed  paint  may  show  no 
and  still  be  absolutely  pure,  for  the  reason  that  the 
metallic  salts  which  have  been  added  to  the  oil  in  the 
form  of  Japan  or  other  siccatives  have  in  a  measure 
saturated  some  of  the  bonds  of  the  linseed  oil,  so  that 
less  iodine  or  bromine  is  absorbed. 


162  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Linseed  oil  dries  by  oxidation,  and  this  oxidation  is 
hastened  by  the  addition  of  bases  or  salts  of  lead  and 
manganese.  There  is  no  doubt  that  some  of  these  act 
catalytically,  and  there  is  likewise  no  question  that  some 
of  these  driers  continue  to  act  long  after  the  oil  is  phys- 
ically dry.  In  drying,  raw  linseed  oil  is  supposed  to 
absorb  as  much  as  18  per  cent  of  oxygen,  but  in  actual 
practice  where  solid  linseed  oil  is  used  as  an  article  of 
commerce  it  seldom  absorbs  more  than  10  per  cent  of 
its  original  weight.  The  addition  of  a  drier  has  much  to 
do  with  the  life  of  a  paint,  there  being  no  two  driers 
that  act  exactly  alike.  If  it  is  the  intention  of  the  paint 
manufacturer  to  make  a  paint  that  will  last  the  longest, 
he  must  study  the  chemical  and  physical  characteristics 
of  the  drier  which  he  uses.  Red  lead  (Pb3O4)  added  to 
linseed  oil  at  a  temperature  up  to  500°  F.,  will  make  a 
very  hard  drying  film  which  in  time  becomes  exceedingly 
brittle.  This  can  be  very  easily  demonstrated  if  the  red 
lead  oil  be  coated  on  cloth  and  its  effect  closely  watched. 
On  the  other  hand,  the  addition  of  litharge  to  linseed  oil 
produces  the  opposite  effect,  and  an  exceedingly  elastic 
film  is  produced.  The  various  manganese  salts  all  act 
differently  and  are  frequently  used  to  excess.  Manganese 
starts  the  drying  operation,  the  lead  salts  continue  it,  and 
the  manganese  again  hastens  the  end.  Borate  of  man- 
ganese is,  perhaps,  the  least  objectionable  of  all  man- 
ganese salts,  but  the  black  oxid  or  peroxid  is  most 
largely  used,  and  if  not  used  in  excess  is  an  exceedingly 
valuable  assistant  in  the  drying  of  linseed  oil. 

These  driers  are  usually  prepared  by  adding  the  oxids 
of  lead  and  manganese  to  melted  rosin.  After  a  resinate 
of  lead  and  manganese  is  produced,  a  small  quantity  of 
linseed  oil  is  added  and  the  mixture  then  cooled  either 
with  turpentine  or  benzine  or  both.  There  are  hundreds 


LINSEED  OIL  163 

of  varieties  of  the  so-called  Japan  driers,  the  best  ones 
containing  the  minimum  amount  of  rosin  and  a  certain 
percentage  of  the  dust  of  Kauri  gum.  The  oil  driers 
are  made  in  a  similar  way,  excepting  that  no  rosin  is- 
used,  and  these  driers  do  the  least  harm.  Lime  is  very 
frequently  used  in  addition  to  oil,  sometimes  in  con- 
junction with  rosin  and  sometimes  alone,  in  order  to 
produce  a  drying  effect.  The  so-called  lime  oil  will  dry 
with  a  hard  and  brittle  film.  The  salts  of  lead  and  man- 
ganese are  not  as  good  for  mixed  paint  purposes  as  they 
are  for  technical  purposes.  The  chloride  of  manganese 
when  added  to  linseed  oil  reacts  upon  it,  and  in  the 
presence  of  any  moisture  in  the  oil  will  liberate  traces  of 
hydrochloric  acid.  Sulphate  of  manganese  and  lead 
acetate  will  act  similarly,  and  wherever  there  is  a  trace  of 
liberated  acid  in  paints  their  rapid  and  uniform  drying 
is  interfered  with.  Zinc  sulphate  and  lead  sulphate  are 
also  excellent  driers.  It  is  considered  good  practice  to  add 
a  small  amount  of  calcium  carbonate  wherever  these 
driers  are  used  in  order  to  neutralize  the  acidity,  and 
\vhen  this  is  done  no  ill  effect  can  be  observed.  Prob- 
ably the  most  flexible  drier  is  Prussian  blue,  which  is 
soluble  in  linseed  oil  at  500°  F.,  and  produces  such  a 
flexible  film  that  the  patent  leather  industry  is  based 
upon  it. 

Some  twenty-three  years  ago  the  author  manufactured 
a  new  drier  which  is  an  improvement  on  Prussian  blue. 
Briefly  described,  this  drier  is  made  out  of  a  by-product 
Prussian  blue  which  is  treated  with  an  alkali  in  the 
presence  of  calcium  oxid  and  water.  A  brown  powder  is 
the  result,  which  has  no  uniformity  of  color  but  has 
given  excellent  results  as  a  drier.  This  brown  has  been 
erroneously  called  "Japanners  Prussian  Brown,"  or 
Japanese  brown.  It  is  soluble  in  linseed  oil  at  500°  F., 


1 64  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

and  produces  a  film  which  is  neither  too  hard  nor  too 
soft,  but  remarkably  elastic  and  admirably  adapted  for 
making  certain  paints  and  varnishes.  It  cannot,  how- 
ever, be  said  to  replace  any  of  the  good  linseed  oil  driers 
for  mixed  paints,  where  too  flexible  a  paint  is  not  desir- 
able, particularly  on  steel  work  or  exterior  work,  as 
blisters  are  likely  to  result  from  the  difference  in  expan- 
sion. However,  as  a  base  for  the  manufacture  of  enamel 
varnishes  and  oils  this  drier  has  proved  itself  admirably 
adapted. 

Linseed  oil  is  a  glyceride  of  several  fatty  acids,  and 
Lewkowitsch  has  proved  that  water  will  replace  the 
glyceride  radical  and  hydrolize  the  oil.  (See  "New  Paint 
Conditions  Existing  in  the  New  York  Subway"  by 
Maximilian  Toch,  Journal  of  the  Society  of  Chemical 
Industry,  No.  10,  Vol.  XXIV.) 

The  action  between  a  fat  and  a  caustic  alkali  in  boil- 
ing solution,  by  which  a  soap  is  formed  and  glycerin  set 
free,  is  too  well  known  to  need  further  discussion.  The 
fatty  acids  which  are  combined  with  the  soda  can  be 
liberated  by  the  addition  of  almost  any  mineral  acid  to 
the  soap.  This  saponification  can  be  produced  by  the 
action  of  water  alone  on  raw  linseed  oil.  Where  a  paint 
contains  lime  or  lead  this  hydrolysis  probably  is  hastened. 

We  have  here  an  excellent  explanation  of  the  so- 
called  porous  qualities,  or  non-waterproof  qualities,  of 
linseed  oil  as  a  paint,  which  is  further  brought  out  by 
the  fact  that  when  linseed  oil  is  treated  with  Prussian 
blue  or  Japanners  Prussian  brown  it  cannot  be  hydrolized 
by  means  of  water,  for  the  acid  radical  has  formed  a  com- 
plete compound  with  the  iron  in  both  of  these  driers,  and 
the  prolonged  heating  has  volatilized  the  glycerin.  Con- 
sequently, when  a  paint  is  made  by  the  treatment  of 
linseed  oil  at  a  temperature  of  over  500°  F.,  with  a 


LINSEED  OIL  165 

neutral  and  soluble  base  like  the  ferri-ferro  cyanide  of  iron, 
the  resulting  film  is  not  linseed  oil  nor  a  linoleate  of  any 
base  with  free  glycerin,  but  a  complex  compound  com- 
posed of  the  various  linseed  oil  acids  united  with  iron. 
This  gives  us  the  basis  of  waterproof  paints.  This  is 
evident  from  the  quality  of  patent  leather,  which  is  not 
only  much  more  flexible  than  any  paint  made  in  the 
ordinary  way,  but  is  likewise  waterproof. 

The  following  are  the  probable  formulas  for  linseed 
oil  in  its  various  stages: 

r  c16H26o2  1 

Ci6H28O2  r  Raw  linseed  oil. 
CistlszOz  J 

C16H2602+Onl 

Ci6H28O2  +  On  \  Japan  and  linseed  oil. 

c18H3202+OnJ 


CieH^Og  +  On  t  Boiled  or  varnish  oil. 

C18H3202+OnJ 

rc16H26o2+oni 

Fe      j  Ci6H28O2  +  On  [  Waterproof  oil. 
l.CisHffiOa+oJ 

There  are  questions  in  regard  to  the  physical  and 
chemical  characteristics  of  linseed  oil  on  which  there  has 
been  considerable  discussion  and  naturally  a  difference 
of  opinion.  The  first  is  whether  linseed  oil  dries  in  a 
porous  film,  and  the  second  is  whether  linseed  oil  while 
drying  goes  through  a  breathing  process  during  which 
it  absorbs  oxygen  and  gives  off  carbonic  acid  and  water. 
With  reference  to  the  porosity  of  the  dry  film  of  linseed 
oil,  the  following  extract  is  made  from  the  Journal  of 
the  Society  of  Chemical  Industry  (May  31,  1905,  "New 
Paint  Conditions  Existing  in  the  New  York  Subway" 
by  Maximilian  Toch). 


1 66  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

"In  a  paper  before  the  American  Chemical  Society 
on  March  20,  1903,  I  gave  it  as  my  opinion  that  a  dried 
film  of  linseed  oil  is  not  porous,  excepting  for  the  air 
bubbles  which  may  be  bedded  in  it,  but  that  any  dried 
film  of  linseed  oil  subjected  to  moisture  forms  with  it  a 
semi-solid  solution,  and  the  moisture  is  carried  through 
the  oil  to  the  surface  of  the  metal.  We  then  have 
two  materials  which  beyond  a  doubt  have  sufficient 
inherent  defects  to  produce  oxidation  under  the  proper 
conditions,  and  granted  that  the  percentage  of  carbon 
dioxid  in  the  air  of  the  tunnel  is  not  beyond  the  normal, 
the  fact  that  carbon  dioxid  together  with  moisture  would 
cause  this  progressive  oxidation  is  sufficient  warrant  for 
the  discontinuance  of  paints  that  are  not  moisture  and 
gas  proof.  Dr.  Lewkowitsch  demonstrated  in  his  Canton 
lectures  that  the  fats  and  fatty  oils  hydrolized  with 
water  alone,  and  linseed  oil  is  hydrolized  to  a  remarkable 
degree  in  eight  hours  when  subjected  to  steam.  It  can, 
therefore,  be  inferred  that  water  will  act  on  linseed  oil 
without  the  presence  of  an  alkali,  and  that  calcium  added 
to  water  simply  hastens  the  hydrolysis  by  acting  as  a 
catalyser.  This,  then,  bears  out  my  previous  assertion 
that  a  film  of  linseed  oil  (linoxyn)  and  water  combine  to 
form  a  semi-solid  solution  similar  in  every  respect  to 
soap,  and  inasmuch  as  we  have  lime,  lead,  iron  and 
similar  bases  present  in  many  paints,  it  is  almost  beyond 
question  that  these  materials  aid  in  the  saponification 
of  oil  and  water." 

If  a  drop  of  linseed  oil  is  spread  on  a  glass  slide  and 
one  half  of  it  covered  with  a  cover  glass,  it  will  be  readily 
seen  under  the  microscope  that  the  dried  film  is  as  solid 
as  the  glass  itself,  that  there  are  no  pores  nor  any 
semblance  to  a  reticulated  structure  visible  in  the  oil, 
and  the  author  therefore  makes  the  statement  with 


No.  45.  D  is  a  glass  flask  of  about  2  litres  capacity.  Through  the  tube  A  3.4  grams  of  refined 
linseed  oil,  which  had  been  heated  to  400  degrees  F.  for  one  hour,  were  introduced  and  well 
distributed  over  the  inner  surface  of  the  flask.  Dry  oxygen  free  from  CO2  was  blown  through 
the  flask,  by  means  of  tubes  A  and  C,  until  the  flask  contained  pure  oxygen.  The  tube  A  was 
then  sealed,  as  shown  in  sketch,  mercury  brought  up  into  the  manometer  by  elevating  B  to  the 
position  shown.  The  flask  was  then  filled  with  oxygen  at  atmospheric  pressure  and  effectually 
sealed.  As  drying  proceeded  and  oxygen  was  absorbed,  the  diminished  pressure  was  read  off 
on  the  manometer.  When  this  became  constant  the  funnel  which  was  connected  to  A  by  a  rubber 
tube  was  filled  with  filtered  Barium  Hydrate  solution,  and  the  point  at  A  broken,  allowing  this 
to  run  into  thfe  flask  without  admission  of  air.  In  a  few  minutes  Barium  Carbonate  was  formed, 
showing  conclusively  that  some  CC>2  had  been  generated  by  the  oil. 

167 


l68  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

absolute  certainty  that  linseed  oil  dries  with  a  homo- 
geneous film  in  all  respects  similar  to  a  sheet  of  gelatin 
or  glue. 

The  question  as  to  whether  linseed  oil  goes  through  a 
breathing  process,  absorbing  oxygen  and  liberating  car- 
bon dioxid  and  water,  is  one  of  great  importance  and 
one  which  the  author  has  worked  out  very  carefully  with 
positive  results.  In  the  illustration  a  piece  of  filter  paper 
two  inches  in  diameter  was  dipped  in  linseed  oil  of  known 
purity  and  suspended  in  a  flask  in  air  absolutely  free 
from  CO2  and  water.  Investigators  have  always  com- 
plained of  the  inability  to  obtain  tight  joints  in  an 
experiment  of  this  kind,  and  in  order  to  be  certain  that 
there  was  no  leakage  all  joints  were  covered  with 
mercury  after  having  been  first  shellacked.  The  mano- 
meter gave  a  curve  which  indicated  the  drying,  a 
thermostat  being  a  part  of  this  instrument,  so  that 
absolutely  uniform  conditions  were  obtained.  At  the 
end  of  thirty  days  the  drying  curve  was  obtained,  and 
when  the  baryta  water  was  led  into  the  bottom  of  the 
flask  there  was  hardly  a  trace  of  turbidity  to  be  noted. 
This  experiment  was  repeated  many  times,  always  with 
the  same  result,  and  the  amount  of  water  or  moisture 
obtained  could  not  be  weighed.  It  was  therefore  reason- 
able to  conclude  that  the  linseed  oil  gave  off  neither  C02 
nor  water,  but  had  absorbed  oxygen. 

The  author,  however,  concluded  that  this  experiment 
was  entirely  too  delicate,  inasmuch  as  only  one  gram  of 
linseed  oil  was  absorbed  by  the  paper.  Therefore,  an 
apparatus  was  devised  as  shown  in  the  illustration, 
without  joints  and  so  absolutely  air-tight  that  the  ques- 
tion of  leakage  could  not  arise.  The  flask  was  filled  with 
linseed  oil  and  then  emptied  by  replacing  the  oil  by  air 
free  from  water  and  CO2,  the  inside  and  bottom  of  the 


LINSEED  OIL  169 

flask  being  left  heavily  coated  with  linseed  oil  which  had 
been  previously  heated  to  400°  F.,  for  one  hour.  The 
manometer  tube  formed  a  part  of  this  apparatus,  and 
when  the  oil  had  dried  completely  (which  was  manifest 
by  its  wrinkled  and  bleached  appearance  and  likewise 
by  the  manometer  indication)  a  rubber  tube  was  attached 
to  the  point  E,  a  funnel  inserted,  and  a  filtered  solution 
of  barium  hydrate  was  allowed  to  run  in  as  soon  as  the 
tip  E  was  broken.  After  ninety  seconds  the  solution  of 
barium  hydrate  turned  milky,  showing  conclusively  that 
C02  had  been  generated  in  the  drying  of  linseed  oil. 

The  next  experiments  were  made  quantitatively,  and 
while  the  amount  of  moisture  could  not  be  accurately 
measured,  the  amount  of  carbon  dioxid  was  in  no  case 
higher  than  T80  of  i  per  cent,  whereas  the  absorption 
of  oxygen  was  19  per  cent.  It  must  therefore  be  admitted 
that  linseed  oil  does  give  off  C02,  but  the  quantity  is 
relatively  so  small  that  it  is  a  question  whether  it  should 
be  taken  into  account  at  all. 

It  is  now  a  known  fact  that  carbon  dioxid  acts  as  a 
rust-producer  on  iron  or  steel,  and  if  linseed  oil  gave  off 
any  appreciable  quantities  of  CO2  and  water  they  would 
act  as  rust-producers  in  themselves  rather  than  pro- 
tectors; and  while  it  may  be  possible  that  some  linseed 
oils  give  off  more  of  these  two  substances  than  others, 
the  amount  under  normal  conditions  cannot  be  very 
great,  as  these  experiments  show. 

Refined  or  bleached  linseed  oil  is  used  to  a  very  great 
extent  for  the  manufacture  of  white  paints.  The  methods 
employed  for  bleaching  linseed  oil  have  not  undergone 
very  much  change  until  lately.  The  coloring  matter  in 
linseed  oil  is  largely  chlorophyll,  the  bleaching  of  linseed 
oil  depending  not  on  the  extraction  of  this  chlorophyll 
but  on  its  change  into  xantophyll,  which  is  yellow. 


No.  46.  DETERMINATION  OF  CO2  AND  H2O  IN  DRYING  OF  LINSEED  OIL  —  A 
piece  of  filter  paper  was  immersed  in  pure  linseed  oil,  and,  after  the  absorbed 
oil  was  weighed,  the  filter  paper  was  suspended  in  the  Erlenmeyer  flask,  on 
the  bottom  of  which  was  a  solution  of  Barium  Hydrate  (free  from  CO2)  to  absorb 
the  CO2  formed  by  the  drying  of  the  oil.  The  flask  was  immersed  in  a  water- 
thermostat,  the  water  of  which  was  stirred  by  a  revolving  mechanical  stirrer. 
A  thermo-regulator,  by  means  of  which  the  gas-flame  under  the  thermostat  was 
automatically  regulated,  was  placed  under  the  flask.  By  opening  the  glass- 
cock,  oxygen  was  admitted  from  time  to  time  to  the  Erlenmeyer  flask,  and  the 
absorption  of  oxygen  was  read  on  the  mercury-manometer.  The  readings  were 
always  made  at  the  same  temperature.  The  oxygen,  before  entering  the  Erlen- 
meyer flask,  was  passed  through  the  KOH  bulb,  where  it  was  washed  free  from 
CO2.  This  experiment  was  conducted  in  triplicate  with  great  care,  the  joints 
being  all  sealed  with  shellac  and  placed  under  mercury.  No  CO2  or  H2O  beyond 
a  trace  could  be  determined,  owing  to  the  small  quantity  of  linseed  oil  which  the 
filter  paper  contained. 

170 


LINSEED  OIL  171 

Sometimes  linseed  oil  will  have  a  reddish  cast  instead 
of  the  usual  greenish  cast.  This  color  is  attributed  to 
another  form  of  organic  matter  known  as  erythrophyll. 
These  three  tints,  the  green,  yellow,  and  red,  are  analogous 
to  the  tints  in  autumn  leaves. 

All  methods  for  extracting  chlorophyll  from  linseed  oil 
have  proved  extremely  difficult  and  expensive.  The  ac- 
cepted method,  therefore,  has  consisted  in  the  treatment  of 
linseed  oil  with  an  acid  in  order  to  convert  the  green  coloring 
matter  into  the  yellow.  This  is  probably  the  reason  why 
no  linseed  oil  exists  which  is  water  white,  although  the 
author  has  made  several  samples  which  are  almost  color- 
less, but  when  compared  in  a  four-ounce  vial  with  chemi- 
cally pure  glycerin  it  can  readily  be  noted  how  far  from 
colorless  the  so-called  bleached  linseed  oil  is.  The  method 
employed  for  bleaching  linseed  oil  consists  in  the  addition 
of  sulphuric  acid  and  the  blowing  of  air  into  the  oil  at 
the  same  time.  The  oil  becomes  cloudy  and  develops 
small  black  clots.  When  this  cloudiness  is  allowed  to 
settle  out,  or  the  oil  is  filtered  through  a  filter  press,  it 
is  very  much  paler  in  color,  and  is  then  known  as  refined 
or  bleached  linseed  oil. 

Sunlight  has  a  similar  effect,  the  oil  produced  by 
bleaching  with  light  and  age  being  superior  in  quality 
to  the  sulphuric  acid  oil.  In  the  sulphuric  acid  treat- 
ment the  oil,  the  water,  and  "foots,"  together  with  an 
appreciable  amount  of  emulsified  oil,  settle  to  the  bottom 
of  the  tank.  These  are  drawn  off,  and  are  of  some  value 
for  making  cheap  barn  paints  by  mixing  with  lime  and 
the  oxids  of  iron.  In  another  method,  which  produces  a 
still  better  bleached  oil,  chromic  acid  is  used.  If  a 
solution  of  this  acid,  which  is  blood  red,  be  added  to 
linseed  oil,  and  the  mixture  agitated,  a  very  much  paler 
and  more  brilliant  oil  is  obtained,  but  it  is  rather 


172  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

expensive  to  produce.  The  treatment  by  means  of  an 
electric  current  in  the  presence  of  moisture  is  likewise 
used  to  some  extent,  but  it  appears  that  this  method  is 
far  more  suited  to  other  oils.  Great  secrecy  is  main- 
tained among  those  who  have  a  knowledge  on  this 
subject.  Peroxid  of  hydrogen  has  likewise  been  recom- 
mended, but  from  the  standpoint  of  cost  the  sulphuric 
acid  method  is  still  the  one  that  is  used  to  the  greatest 
extent. 

The  new  methods  which  are  favorably  spoken  of,  and 
which  the  author  has  found  to  be  inexpensive  and 
efficient,  involve  the  use  of  the  peroxids  of  calcium, 
magnesium,  and  zinc.  These  peroxids  are  made  into 
paste  with  water,  one  pound  being  sufficient  for  200 
gallons  of  linseed  oil.  This  amount  of  oil  is  placed  in 
an  open  kettle  or  vat,  together  with  the  peroxid,  and 
thoroughly  agitated.  During  agitation  a  strong  solution 
of  sulphuric  acid  is  added,  which  liberates  nascent  oxygen. 
If  the  oil  be  allowed  to  settle,  or  is  filtered,  and  is  then 
heated  to  drive  off  any  traces  of  moisture,  a  very  brilliant 
pale  oil  is  obtained. 

It  has  always  been  understood  that  linseed  oil  con- 
tained albuminous  matter  which  coagulated  at  a  tem- 
perature of  400°  F.,  or  over,  and  produced  a  flocculent 
mass.  When  an  oil  answered  this  reaction  it  was  said 
to  "break"  at  the  low  temperature  and  was  useless  for 
making  varnish  oil  and  other  high  grades  of  linseed  oil. 
G.  W.  Thompson  found  that  this  break  was  not  due 
to  the  presence  of  albuminous  and  nitrogenous  matter, 
but  that  it  was  caused  by  the  separation  of  several 
phosphates.  This  explanation  has  generally  been  ac- 
cepted as  correct.  If  an  oil,  therefore,  is  allowed  to  age, 
the  phosphates  settle  out  and  the  oil  does  not  break. 
Cold-pressed  linseed  oil,  if  it  breaks  at  all,  does  not  break 


LINSEED  OIL  173 

at  as  low  a  temperature  as  hot-pressed  oil.  Bleached 
linseed  oil  does  not  wear  as  well  as  the  oil  that  has  been 
clarified  by  standing. 

The  demand  for  brilliant  white  paints  or  brilliant 
enamels  is  responsible  for  the  manufacture  of  the  so- 
called  water-white  oils.  From  a  large  variety  of  tests 
made  by  the  author  it  was  fully  demonstrated  that 
white  paints  composed  of  mixtures  of  pigments  such 
as  sublimed  lead,  zinc  oxid,  and  white  lead  all  showed 
absolutely  the  same  whiteness  within  two  weeks  after 
they  were  exposed  to  the  light,  irrespective  of  the 
kind  of  raw  linseed  oil  used.  One  of  the  five  tests 
was  made  with  a  paint  prepared  with  a  linseed  oil  that 
had  not  been  aged  for  more  than  two  months,  but 
within  the  time  mentioned  it  was  just  as  white  as  the 
rest. 

Linseed  oil  paints  are  supposed  to  deteriorate  after 
a  few  years  and  lose  their  value,  owing  to  the  decomposi- 
tion of  linseed  oil.  This  statement  is  questionable,  and 
while  there  is  no  doubt  that  the  ready-mixed  paint 
thickens  and  changes  slightly  in  its  chemical  and  physical 
characteristics,  the  change  is  exceedingly  small  in  a  con- 
tainer which  is  hermetically  sealed.  There  is  no  doubt 
in  regard  to  the  reaction  which  takes  place  between  the 
oil  and  white  lead,  zinc  oxid,  and  a  number  of  the 
unstable  compounds  in  a  mixed  paint.  While  these 
reactions  are  very  slow,  they  are  at  the  same  time  very 
definite.  If  the  value  of  a  paint  were  reduced  to  a 
curve  it  would  probably  be  found  that  the  curve  would 
be  represented  by  the  arc  of  a  large  circle  approaching 
a  straight  line.  As  far  as  paste  paints  are  concerned, 
particularly  white  lead,  all  painters  prize  white  lead  more 
highly  when  it  is  old  than  when  it  is  fresh. 


174  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Typical  Analysis  of  Bleached,  Refined  Linseed  Oil 

Specific  Gravity 932-. 934 

Iodine  Value  (Harms) Above  180 

Saponification  Value 190-194 

Acid  Value 3-5 

STANDARD  SPECIFICATIONS.  AMERICAN  SOCIETY  FOR  TESTING 
MATERIALS,   1914^.335 

Purity  of  Raw  Linseed  Oil  from  North  American  Seed 
Properties  and  Tests 

i.  Raw  linseed  oil  from  North  American  seed  shall  conform  to 
the  following  requirements: 

Max.  Min. 

Sp.  gr.— — 0  C 0.936  0.932 

2S° 
or  — i  C -. 0.931  0.927 

25 

Acid  Number 6.00 

Saponification  Number 195.               189. 

Unsaponifiable  —  per  cent 1.50 

Refractive  Index  at  25°  C 1-4805           1.4790 

Iodine  No.  (Hanus) 178. 

A  linseed  oil  may  however  be  pure  if  the  iodine  num- 
ber is  165  and  it  may  be  just  as  pure  if  the  iodine  num- 
ber is  195.  The  latter  number  was  prevalent  in  the  crop 
of  1913. 

STANDARD  SPECIFICATIONS  FOR  BOILED  LINSEED  OIL  FROM 
NORTH  AMERICAN  SEEDX 

Properties  and  Tests 

i.  Boiled  linseed  oil  from  North  American  seed  shall  conform 
to  the  following  requirements: 

1  American  Society  for  Testing  Materials,  1915,  p.  420. 


LINSEED  OIL  !75 

0  Max.  Min. 

Specific  Gravity  -^  C 0.945          0.937 

J5-5 
Acid  Number 8. 

Saponification  Number 195.  189. 

Unsaponifiable  Matter,  per  cent 1.5 

Refractive  Index  at  25°  C 1.484  1-479 

Iodine  Number  (Hanus) 178. 

Ash,  per  cent 0.7  0.2 

Manganese,  per  cent ...  0.03 

Calcium,  per  cent 0.3 

Lead,  per  cent o.i 

NAVY  DEPARTMENT  SPECIFICATIONS 

BOILED  LINSEED  OIL 

Composition 

1.  Boiled  linseed  oil  shall  be  absolutely  pure  boiled  oil  of  high 
grade,  made  wholly  by  heating  pure  linseed  oil  to  over  350°  F.  with 
oxids  of  lead  and  manganese  for  a  sufficient  length  of  time  to  secure 
proper  combination  of  the  constituents  and  be  properly  clarified  by 
settling  or  other  suitable  treatment.     Evidence  of  the  presence  of  any 
matter  not  resulting  solely  from  the  combination  of  the  linseed  oil 
with  the  oxids  of  lead  and  manganese  will  be  considered  grounds  for 
rejection. 

Chemical  Constants 

2.  The  oil  shall  upon  examination  show: 

Unsaponifiable  matter Not  more  than  1.5  per  cent. 

Lead  oxid  (PbO) Not  less  than  0.20  per  cent. 

Manganese  oxid  (MnO) ....  Not  less  than  0.04  per  cent. 

Iodine  No.  (Hanus) Not  less  than  178. 

Specific  gravity  at  60°  F  . .  .  Not  less  than  0.938. 

The  oil  shall  give  no  appreciable  loss  at  212°  F.  in  a  current  of 
hydrogen. 

Physical  Characteristic 

3.  When  flowed  on  glass  and  held  in  a  vertical  position,  the  oil 
shall  dry  practically  free  from  tackiness  in  12  hours  at  a  temperature 
of  70°  F. 


176  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Basis  of  Purchase 

4.  To  be  purchased  by  the  commercial  gallon;    to  be  inspected 
by  weight,  and  the  number  of  gallons  to  be  determined  at  the  rate  of 
1\  pounds  of  oil  to  the  gallon. 

Quantity,  How  Determined 

5.  The  quantity  of  oil  delivered  in  5-gallon  shipping  cans  will  be 
determined  by  taking  the  gross  weight  of  10  per  cent  of  the  total 
number  of  cans,  selected  at  random,  from  which  the  average  gross 
weight  of  the  delivery  will  be  determined.     A  sufficient  number  of 
these  cans  will  be  emptied  to  determine  the  average  tare,  and  the  net 
weight  of  the  oil  will  be  taken  from  the  figures  thus  obtained. 

STAND  OIL 

Stand  oil  is  a  very  heavy,  viscous  form  of  linseed  oil 
which  has  great  use  in  the  arts  for  the  manufacture  of 
both  air  drying  and  baking  enamels.  It  is  supposed  that 
it  originated  in  Holland,  but  there  is  a  difference  of 
opinion  on  this  for  the  reason  that  the  table  oilcloth 
manufacturers  in  Scotland  made  a  similar  oil  under  the 
name  of  "marble  oil"  long  before  the  Dutch  made  any 
enamel  paints. 

The  method  of  making  marble  oil,  which  is  a  form 
of  stand  oil,  is  simply  to  heat  a  linseed  oil  which  has 
no  "break"1  to  550°  F.,  and  to  keep  it  at  that  tem- 
perature or  slightly  over  until  it  becomes  very  heavy 
and  viscous.  Its  specific  gravity  changes  from  .930  to 
.980,  at  which  point  a  small  quantity  placed  on  a  piece 
of  glass  and  allowed  to  cool  piles  or  stands  up  in  a  little 
mound  and  runs  very  slowly.  With  the  oil  still  at  550° 
F.,  a  small  quantity  of  litharge  is  added;  this  is  known 
as  adding  the  drier  on  the  downward  cool,  which  simply 

1  An  oil  from  which  no  black  flocculent  particles  separate  at 
500°  F.  is  technically  known  as  an  oil  which  has  no  "break"  or 
does  not  "break." 


LINSEED  OIL  177 

means  that  the  oil  takes  up  the  drier  not  as  the  heat  is 
increasing  but  as  the  heat  is  decreasing.  The  amount 
of  litharge  added  is  necessarily  very  small,  because  if 
more  than  one  tenth  of  i  per  cent  be  added  the  oil 
becomes  considerably  darkened,  while  the  object  in 
making  an  enamel  oil  or  marble  oil  is  to  retain  its  color. 
Oil  made  solely  with  litharge  as  a  drier  dries  very  tacky 
and  must  be  baked  to  at  least  110°  F.  for  several  hours 
before  it  will  dry  entirely.  For  this  reason  many  add  a 
small  percentage  of  borate  of  manganese  with  the  lith- 
arge, or  chloride  and  sulphate  of  manganese,  as  a  drier. 

Of  all  the  driers  for  making  stand  oil  for  enamel 
paints  cobalt  is  the  best,  for  a  very  small  quantity  is 
necessary  to  perform  the  function  of  drying  and  no  bad 
results  are  obtained.  Where  manganese  driers  are  used 
and  continued  oxidation  takes  place  a  white  enamel 
paint  may  turn  entirely  pink,  due  to  the  formation  of  a 
manganese  salt  of  that  color.  Where  lead  is  used  slow 
and  sticky  drying  may  result,  but  where  lead  and 
manganese  are  used  together  in  dark  colored  enamels 
excellent  results  are  obtained  and  any  change  in  color 
value  is  not  noticed. 

Some  stand  oils  are  made  also  by  partial  oxidation  or 
blowing  and  partial  heating.  These,  however,  are  short, 
and  when  placed  between  the  thumb  and  forefinger  and 
rubbed  rapidly  do  not  form  a  long  thread  but  a  short 
thread.  Experience  has  taught  that  a  short  oil  is  short 
lived  and  a  long  oil  is  long  lived.  There  is  obviously  a 
good  reason  for  this,  as  the  short  oil  has  been  highly 
oxidized  and  continues  to  oxidize  after  it  is  dry.  Yet  for 
interior  enamel  purposes  a  short  enamel  oil  will  last  many 
years. 

One  of  the  best  features  of  enamel  oil  or  stand  oil  is 
that  brush  marks  even  with  a  poor  brush  are  eliminated 


1 78  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

and  flow  together.    Zinc  oxid  is  the  principal  pigment  used 
in  the  manufacture  of  all  of  these  enamel  paints. 

JAPANNER'S  PRUSSIAN  BROWN  OIL 

This  is  a  stand  oil  or  marble  oil  identical  in  all 
respects  with  that  described  under  the  heading  "Stand 
Oil,"  excepting  that  it  is  dark  in  color  and  therefore 
only  used  for  making  dark  colored  enamels  such  as 
patent  leather,  machinery  enamels  and  waterproof  coat- 
ings which  must  have  a  high  glaze. 

The  method  used  for  making  this  oil  depends  very 
largely  upon  the  good  quality  of  the  linseed  oil,  and  the 
oil  must  have  no  tendency  to  "break"  whatever.  It 
must  be  heated  to  550°,  at  which  temperature  three 
ounces  dry  or  six  ounces  in  oil  of  Japanner's  Prussian 
Brown  are  added  slowly  until  the  oil  which  at  first  is 
muddy  becomes  clear  and  of  the  color  and  consistency 
of  dark  honey. 

As  the  present  tendency  is  to  varnish  or  enamel 
automobile  parts  and  bake  them  at  fairly  high  tempera- 
tures this  oil  has  become  of  great  value,  particularly  when 
mixed  with  a  fossil  resin  varnish,  and  as  there  are  but 
very  few  automobiles  which  are  painted  white  the  dark 
color  of  this  particular  oil  is  no  objection. 

For  the  manufacture  of  an  enamel  paint  for  painting 
engines  which  are  continually  at  a  temperature  of  be- 
tween 170°  and  212°  F.  on  account  of  being  water  jacketed, 
it  has  been  found  that  the  dark  enamels  used  for  this 
purpose  when  made  with  the  Japanner's  Brown  oil 
containing  at  least  25  per  cent  of  a  high  grade  fossil 
resin  varnish  give  results  that  are  astonishing.  Enamel 
paints  on  an  engine,  composed  of  the  materials  just 
described,  will  at  the  end  of  a  year  be  practically  as  good 
as  the  day  that  they  were  applied. 


LINSEED  OIL  179 

Typical  Analysis  of  Heavy  Bodied  Blown  Oil 

Specific  Gravity 988-.Q93 

Saponification  Value 195-210 

Iodine  Value 100-140 

Acid  Value 4-6 

Typical  Analysis  of  Enamel  Oil 

Specific  Gravity .9678 

Iodine  Value 174-5 

Saponification  Value iQ5-o 

Acid  Value 7.3 


CHAPTER   XIII 
CHINESE  WOOD  OIL 

CHINESE  wood  oil  (China  wood  oil),  or,  as  it  is  some- 
times known,  Japanese  wood  oil  or  Tung  oil,  is  very  largely 
used  in  the  United  States,  but  there  appears  to  be  very 
much  secrecy  with  reference  to  its  manipulation. 

It  is  a  peculiar  fact  that  the  majority  of  writers  on  this 
oil  are  inclined  to  condemn  it,  for  the  principal  reason 
that  when  China  wood  oil,  as  it  is  commonly  called,  is 
brushed  out  on  a  sheet  of  glass  it  dries  in  about  12  hours 
to  an  opaque  film  which  presents  a  rough  appearance 
and  does  not  adhere  very  well  to  the  glass.  It  is  per- 
fectly true  that  this  is  a  characteristic  of  China  wood  oil, 
and  it  is  likewise  true  that  it  has  no  elasticity  and  that 
its  waxlike  appearance  after  drying  condemns  it  very 
thoroughly,  but  it  only  goes  to  prove  the  difference 
between  theory  and  practice,  for,  whereas  China  wood 
oil  in  its  raw  state  is  totally  unfit  for  use  and  spoils  any 
good  paint  to  which  it  may  be  added,  when  properly 
treated  it  is  one  of  the  most  remarkable  paint  assistants 
which  we  have,  and  those  who  have  studied  the  subject 
carefully  have  made  very  successful  paints. 

It  might  be  proper  to  cite  as  a  parallel  case  that  it 
would  be  manifestly  unfair  to  condemn  meat  as  an  article 
of  diet  for  the  reason  that  it  is  tough,  difficult  to  mas- 
ticate, insipid  in  its  taste,  and  hard  to  digest.  On  the 
other  hand,  the  excellent  flavor  and  nutritious  qualities 
of  meat  which  has  been  properly  cooked  and  seasoned 

totally    disproves    the    first    statement.     It    is    evidently 

1 80 


CHINESE  WOOD  OIL  181 

very  unfair  to  compare  raw  meat  with  properly  cooked 
meat. 

In  the  winter  time,  at  ordinary  freezing  temperature, 
China  wood  oil  looks  like  a  mixture  of  tallow  and  sand 
and  has  a  similar  consistency.  The  head  of  the  cask  is 
removed,  the  oil  cut  out  in  slices  and  put  into  a  kettle 
for  treatment. 

It  is  pretty  well  agreed  that  at  450°  F.  China  wood 
oil  gelatinizes,  and  if  allowed  to  cool  becomes  insoluble. 
But  experts  in  the  manipulation  of  China  wood  oil  add 
metallic  salts  or  resinates  at  this  temperature  and  a 
small  percentage  of  untreated  linseed  oil,  and  before  it  is 
sufficiently  cool  small  quantities  of  naphtha  and  benzol. 
The  resulting  liquid  is  a  clear  varnish-like  oil  which  dries 
with  a  hard  elastic  film,  much  more  slowly  than  the 
original  China  wood  oil.  In  this  condition  it  possesses 
most  remarkable  qualities. 

By  the  use  of  China  wood  oil  paints  are  made  which 
dry  in  damp  atmospheres.  The  advantage  which  the 
Chinese  and  Japanese  have  had  over  the  Europeans  on 
this  subject  has  been  recognized  for  a  long  time.  It  is 
now  known  to  have  been  due  to  their  knowledge  of  the 
proper  manipulation  of  China  wood  oil.  For  the  making 
of  marine  paints  and  waterproof  paints  China  wood  oil  is 
indispensable. 

In  the  United  States  preference  is  given  to  two  brands 
of  China  wood  oil;  one  is  called  the  Hankow  and  the 
other  the  Canton,  the  Hankow  being  the  better  of  the 
two.  The  Canton  oil  is  darker,  and  it  is  very  likely  that 
it  is  expressed  from  the  seed  by  a  hot  process,  whereas 
the  Hankow  oil  is  expressed  by  the  cold  process. 

The  chemical  constants  of  China  wood  oil  are  about 
the  same  as  those  of  linseed  oil,  its  specific  gravity  being 
slightly  higher  in  the  third  decimal,  its  iodine  value  rather 


182  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

lower,  and  its  saponification  number  almost  the  same.  The 
oil  has,  however,  a  characteristic  odor  which  cannot  be 
easily  destroyed,  and  a  paint  manufacturer  who  is  once 
familiar  with  this  odor  can  never  be  deceived.  At  the 
same  time,  where  a  small  quantity  of  China  wood  oil  is 
used  for  the  purpose  of  making  a  particular  kind  of  cal- 
cium oleate,  it  loses  its  characteristic  odor.  The  calcium 
oleate  so  obtained  is  eventually  split  up  by  atmospheric 
moisture,  and  is  therefore  valuable  for  making  a  cement 
paint  which  has  been  patented.1 

China  wood  oil  is  largely  used  in  the  making  of  enamel 
paints.  Such  paints  give  perfect  satisfaction,  last  longer, 
and  wear  better  than  many  of  the  resin  varnish  enamels. 
This  work  does  not  treat  of  enamel  paints,  although  these 
paints  could  be  classed  as  mixed  paints,  because  they  are 
a  mixture  of  varnish  or  oil  and  pigment.  As  the  ratio  of 
the  ingredients  is  totally  different  from  that  of  oil-mixed 
paints,  the  subject  of  the  use  of  China  wood  oil  in  these 
enamels  has  no  place  in  this  chapter.  Where  a  manu- 
facturer is  at  liberty  to  use  any  material,  China  wood 
oil  can  in  no  sense  be  regarded  as  an  adulterant.  It  is 
more  expensive  than  linseed  oil  and  only  on  one  or  two 
occasions  has  the  price  of  linseed  oil  approximated  that 
of  China  wood  oil,  but  even  if  the  two  in  their  raw  state 

1  The  constants  of  a  sample  of  China  wood  oil  were  compared  with 
those  of  linseed  oil  in  1906,  and  it  is  of  interest  to  know  that  the  same 
sample  was  reanalyzed  by  the  author  in  1915,  with  the  following 
results. 

1906  1915 

0-935 Sp.  gr.          =  0.953  at  60°  F. 

Acid  Value  =  8.1 

190 Sapon.  Val.  =  194.7 

165 Iodine  Val.  =  146.6 

The  oil  was  kept  in  a  glass-stoppered  bottle.  It  had  become  very 
thick,  viscous  and  clear. 


CHINESE  WOOD  OIL  183 

were  exactly  the  same  in  price,  China  wood  oil  would  be 
very  much  dearer  eventually  on  account  of  the  high  cost 
of  manipulation.  All  factory  experience  indicates  that 
the  manipulation  of  China  wood  oil  increases  its  cost  20 
per  cent  if  based  on  a  cost  price  of  50  cents  per  gallon, 
whereas  by  the  same  manipulation  the  price  of  linseed 
oil  would  be  increased  only  5  per  cent. 

Tung  oil  is  probably  the  glyceride  of  two  acids  — 
elaeomargaric  and  oleic,  while  linseed  oil  is  probably  the 
glyceride  of  three  acids.  China  wood  oil  has  two  peculiar 
qualities  which  make  it  very  valuable  for  the  manu- 
facture of  floor  paints.  The  first  is,  its  resistance  to 
moisture,  and  the  second,  its  extreme  hardness  so  that 
it  does  not  show  scratch  marks.  For  the  manufacture 
of  floor  paints  for  railway  and  steamship  use,  these 
two  qualities  are  essential.  On  the  ferry-boats  floating 
in  the  rivers  of  the  United  States  it  is  customary  to  wash 
the  floors  several  times  a  day.  A  linseed  oil  paint  soon 
becomes  spongy  and  is  destroyed  by  this  treatment.  A 
floor  paint  composed  of  a  large  amount  of  China  wood 
oil  and  a  small  amount  of  resin  does  not  show  a  heel 
mark  very  readily,  which  is  a  decided  advantage. 

The  Japanese  are,  however,  more  adept  in  the  manip- 
ulation of  China  wood  oil  than  any  other  nation.  The 
author  has  three  samples  of  varnish  oil,  one  of  which 
has  almost  the  consistency  and  appearance  of  chemically 
pure  glycerin.  It  has  a  faint  yellowish  tinge,  and  while 
it  is  no  better  in  its  physical  characteristics  than  the 
nominally  treated  China  wood  oil,  it  indicates  that 
without  destroying  any  of  its  good  qualities  the  Japanese 
can  prepare  this  oil  for  lacquer  and  enamel  purposes  until 
it  is  practically  water  white. 

It  is  a  known  fact  that  there  has  been  great  secrecy 
among  the  paint  and  varnish  makers  on  the  question  of 


184  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

China  wood  oil,  and  those  who  have  used  it  successfully 
have  forged  ahead  of  their  competitors.  Its  moderate 
use  in  a  waterproof  paint  or  damp-proof  paint  is  of  great 
benefit.  Its  use  as  a  mixing  varnish  or  combining 
medium  in  mixed  paints  is  likewise  of  great  value. 

In  its  constants  it  is  analogous  to  linseed  oil,  and  it 
always  has  a  most  characteristic  odor  by  which  it  can  be  in- 
variably distinguished.  It  is,  however,  frequently  subjected 
to  adulteration  with  cheaper  oils,  and  one  of  the  first 
samples  the  author  ever  received  was  shipped  from  China 
in  a  5-gallon  kerosene  tin  which  contained  a  considerable 
quantity  of  kerosene,  either  accidentally  or  intentionally. 
The  oil  from  Canton,  according  to  the  experience  of  the 
author,  is  by  no  means  as  good  as  the  oil  from  Hankow, 
the  Hankow  oils  being  paler  in  color  and  responding 
more  clearly  to  the  accepted  chemical  constants.  One 
of  the  best  tests  for  the  determination  of  the  purity  of 
China  wood  oil  is  to  heat  it  very  slowly  in  boiling  water 
for  an  hour;  then  transfer  the  test  to  a  naked  flame  and 
heat  it  for  twenty  minutes  to  450°  F.  Some  care  must 
be  exercised  not  to  flash  the  oil  nor  to  char  it.  It  is 
then  allowed  to  cool,  a  good  method  being  to  place  it  in 
cold  water  for  half  an  hour,  after  which  time  the  oil 
must  assume  the  appearance  of  an  almost  solid  gelatin. 
The  admixture  of  any  adulterant,  particularly  cotton- 
seed oil,  prevents  the  coagulation  or  semi-solidification 
of  China  wood  oil. 

In  order  to  manipulate  China  wood  oil  for  paint 
it  must  be  treated  with  an  organic  acid  salt  of  lead 
and  manganese  which  is  sold  for  the  purpose.  A 
number  of  paint  manufacturers  have  treated  China 
wood  oil  with  great  success  in  the  following  manner:  10 
gallons  of  China  wood  oil  are  slowly  heated  in  a  copper 
kettle  to  350°  F.,  and  10  pounds  of  this  organic  salt  are 


CHINESE  WOOD  OIL  185 

added.  When  entirely  dissolved,  which  takes  but  a  very 
short  time,  5  gallons  of  refined  linseed  oil  are  slowly 
stirred  in  and  the  whole  heated  to  400°  F.  and  kept  at 
that  temperature  for  half  an  hour.  The  kettle  is  now 
withdrawn  from  the  fire,  and  i\  gallons  of  either  tur- 
pentine or  benzine,  or  a  mixture  of  both,  are  added. 
This  oil,  known  as  China  base  oil,  is  then  used  in  varying 
proportions  in  mixed  paints  for  smoke  stacks,  floor 
paints,  and  varnishes,  according  to  the  experience  or 
knowledge  of  the  manufacturer. 

The  chemical  detection  of  China  wood  oil  is  still 
somewhat  empirical  when  it  is  contained  in  paints  or 
varnishes.  Some  years  ago  the  author  made  the  state- 
ment that  China  wood  oil  could  always  be  identified  to 
a  greater  or  lesser  degree  on  account  of  its  "heathen" 
odor.  Anyone  familiar  with  China  wood  oil  or  while 
cooking  it  can  identify  it  at  once.  This  may  be  em- 
pirical, but  it  is  just  as  positive  as  the  odor  of  fish 
oil  when  heated,  and  as  the  chemist-  has  to  depend  to 
quite  some  extent  upon  his  sense  of  taste  and  smell, 
the  sense  of  smell  when  heating  a  varnish  under  exam- 
ination is  a  fair  guide  when  oils  which  have  a  specific 
odor  are  contained. 

Formerly  very  little  attention  was  paid  to  the  acid 
figure  of  China  wood  oil,  but  today  this  acid  figure  plays 
a  very  prominent  role.  It  is  definitely  known  now  that 
the  high  acid  number  of  China  wood  oil  prevents  it 
from  being  used  for  making  enamel  varnishes  where  zinc 
or  lead  is  used,  for  the  reason  that  these  pigments  act 
as  bases  and  thicken  the  resulting  enamel  paint.  It  is 
therefore  either  necessary  to  neutralize  the  acids  or  to 
use  a  pigment  which  is  not  attacked,  like  lithopone. 

The  polymerization  of  China  wood  oil  is  not  under- 
stood. According  to  the  patent  of  Beringer  the  addition 


186  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

of  a  sulphur  compound  prevents  the  polymerization.  The 
author  has  made  experiments  using  barium  sulphide  and 
finds  that  i  per  cent  of  barium  sulphide  prevents  poly- 
merization, but  the  addition  of  any  one  of  these  materials, 
including  sulphur  or  selenium  compounds,  paralyzes,  the 
drying  quality  of  China  wood  oil. 

China  wood  oil  plays  a  very  important  role  in  the 
manufacture  of  flat  wall  paints  and  neutralizing  fillers 
and  varnishes  for  the  painting  of  Portland  cement. 
From  the  analyses  of  various  types  of  China  wood  oil 
that  have  come  to  the  laboratory  of  the  author  it  was 
noted  that  its  acid  number  is  considerably  higher  than 
that  of  linseed  oil,  and  therefore  care  must  be  taken  in 
the  selection  of  the  pigments  with  which  China  wood  oil 
is  ground,  or  else  livering  will  ensue.  As  for  instance,  in 
the  making  of  an  enamel  paint  in  which  zinc  oxid  is  used, 
the  enamel  paint  may  keep  in  suspension  or  be  preserved 
as  a  ready  mixed  paint  for  several  weeks,  but  at  the  end 
of  a  week  it  will  gradually  grow  thicker  until  finally  it 
becomes  too  thick  for  use.  This  is  due  entirely  to  the 
fact  that  the  free  organic  acid  of  the  China  wood  oil 
combines  with  the  zinc  or  other  base  and  forms  a  com- 
pound. In  order  to  overcome  this  a  fair  knowledge  of 
the  chemistry  of  the  pigments  is  necessary,  and  neu- 
tralization of  the  China  wood  oil  must  first  take  place 
before  it  is  heated  or  converted  into  a  varnish  oil. 

In  a  previous  chapter  which  was  written  nearly  ten 
years  ago  the  author  made  the  statement  that  raw 
China  wood  oil  is  not  used  to  any  great  extent;  in  fact, 
it  has  always  been  regarded  that  raw  China  wood  oil  is 
decidedly  unfit  for  use  and  spoils  any  paint  to  which  it 
may  be  added,  but  since  the  flat  wall  paints  and  the 
Portland  cement  paints  have  come  into  use  the  addition 
of  a  small  percentage  of  raw  China  wood  oil  has  been 


CHINESE  WOOD  OIL  187 

found  beneficial  not  only  for  producing  flat  surfaces  but 
for  producing  a  surface  upon  which  a  subsequent  coat 
of  paint  will  adhere  better  than  it  would  to  a  surface 
which  contained  no  raw  China  wood  oil. 

China  wood  oil  has  particularly  good  qualities  for 
coating  Portland  cement  surfaces,  but  this  invention  is 
fully  covered  by  patent1. 

In  the  manufacture  of  baking  enamels  most  excellent 
results  have  been  obtained  where  China  wood  oil  is 
prepared  with  soya  bean  oil  at  a  temperature  of  520°  F. 
with  or  without  the  presence  of  resins  or  rosin.  Rosin, 
of  course,  is  not  recommended  in  any  high  grade  baking 
or  stoving  varnish,  because  it  will  distill  and  produce 
either  a  flat  surface  or  one  which  will  alligator,  but  the 
fossil  or  semi-fossil  resins  when  added  to  a  mixture  of  these 
two  oils  produce  baking  varnishes  which  are  particularly 
good  for  the  hoods  of  automobiles  or  the  radiators,  which 
are  alternately  hot  and  cold. 


A  METHOD  FOR  THE  DETECTION  OF  ADULTERATION  OF 
CHINA  WOOD  OiLS.2 

"About  July  15,  1912,  there  appeared  a  paper  pub- 
lished by  the  New  York  Produce  Exchange,  which  spoke 
of  the  Bacon  method  for  the  detection  of  at  least  5  per 
cent  adulteration  of  China  wood  oils.  The  paper  set  forth 
that  the  suspected  oils  were  to  be  placed  in  a  bath  of 
between  280°  and  285°  C.  for  8|  or  9  minutes.  To  detect 

1  U.  S.  Letters  Patent  No.  813,841. 

1  This  paper  was  presented  by  Louis  S.  Potsdamer  before  the 
Eighth  International  Congress  of  Applied  Chemistry,  1912,  Section 
Ve,  "Paints,  Drying  Oils  and  Varnishes,"  of  which  the  author  was  the 
President.  This  paper  was  written  under  the  direction  of  the  author 
and  emanated  from  the  research  laboratory  of  Toch  Brothers. 


l88  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

adulteration  after  polymerization  the  oils  were  to  be  cut 
with  a  knife,  the  pure  offering  little  or  no  resistance  to 
cutting  and  showing  a  clean  cut  surface ;  while  the  adul- 
terated under  similar  treatment  displayed  a  ragged  cut, 
or  else  it  could  not  be  cut  at  all. 

This  was  given  a  fair  trial  in  the  research  laboratory 
of  Toch  Brothers'  paint  factory,  with  little  success,  until 
I  decided  to  note  the  temperature  of  polymerization  of 
the  various  samples,  adulterated  and  pure.  I  had 
several  samples  of  the  pure  oil,  and  these  I  made  up  into 
stock  solutions  as  follows: 

» 

Pure, 

5  %  Adulteration  with  Soya  Bean  Oil 

10%  "  "        "        "       " 

7%  "     Paraffin  Oil 

10% 

(Soya  bean  and  paraffin  oils  were  chosen  as  representative  of  vege- 
table and  mineral  oils  respectively.) 

The  apparatus  used  was  such  that  a  bath  of  oil 
(pure  soya  bean  oil)  was  placed  in  a  nickel  pot  of  about  8 
inches  diameter.  In  this  were  suspended  two  test  tubes, 
arranged  to  act  as  an  air  bath.  The  samples  were  placed 
in  tubes  of  slightly  smaller  bore,  and  in  turn  in  the  air 
bath.  Thermometers  were  suspended  in  these  tubes  so 
that  the  mercury  bulbs  extended  below  the  middle  of  the 
oil  under  examination. 

The  bath  was  first  heated  to  a  temperature  be- 
tween 510°  and  525°  F.,  and  the  sample  tubes,  filled 
so  that  the  oil  surface  did  not  extend  above  the  sur- 
face of  the  bath,  then  placed  in  position.  They  were 
allowed  to  remain  in  this  position  until  polymerization 
just  set  in,  stirring  once  in  a  while  with  the  ther- 
mometers. 


CHINESE  WOOD  OIL  189 

At  the  point  of  polymerization  the  temperature  was 
noted  and  the  tubes  withdrawn  from  the  bath.  Referring 
to  the  tables  one  can  see  that  adulterations  as  low  as  5 
per  cent  cause  a  very  perceptible  drop  in  the  temperature 
of  polymerization. 

I  made  only  three  sets  of  oils,  but  from  these  I 
obtained  results  on  which  I  base  my  method  for  the 
detection  of  adulteration.  I  found  that  the  first  two  oils 
under  examination  had  an  average  polymerization  tem- 
perature of  553°  and  the  third  (a  mixture  of  two  sup- 
posedly pure  oils  received  at  Toch  Brothers'  factory  for 
testing)  a  somewhat  lower  temperature. 

Disregarding  such  a  small  discrepancy,  15°  F.,  we 
notice  that  the  adulteration  caused  a  decided  drop  in 
the  polymerization  temperature,  and  as  soya  bean  oil 
is  handiest  to  the  oriental,  we  may  expect  adulteration 
with  this. 

By  the  method  herein  described,  an  adulteration  of 
5  per  cent  could  be  detected.  To  settle  this  finally  I 
offer  this  suggestion:  that  the  American  Society  for 
Testing  Materials  now  working  on  the  standardization 
of  soya  bean  and  China  wood  oils  add  the  above  to 
their  tests  and  so  obtain  a  standard  temperature  of 
polymerization  in  the  manner  described,  and  all  oils 
meeting  such  a  temperature  (or  those  within  a  small 
range)  call  pure.  It  would  then  be  a  very  simple  matter 
to  detect  adulteration. 

Supplementing  the  polymerization  test  the  specific 
gravities  of  the  oils  were  determined  under  standard 
conditions  (60°  F.).  It  was  noticed  that  the  higher  the 
percentage  of  adulteration  the  lower  the  specific  gravity, 
and  further,  when  the  adulteration  was  mineral  oil  the 
specific  gravity  was  lowered  at  least  four  times  as  much 
as  with  a  similar  percentage  of  vegetable  oil. 


i  go 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


POLYMERIZATION  TEMPERATURES 


Sample 
Pure               

Set  i 
Aver. 

'55i       553 

Set 
552 

2 

Aver. 

553 

Set 
538 

3 

Aver. 

537 

5  %  Soya  Bean  Oil 
adulteration  

1554 
522       519 
516 

554 

520 

5x7 

535 
505 

CQO 

503 

10%  Soya  Bean  Oil 
adulteration  

502       500 
4.08 

476 

4.74. 

475 

498 

CQO 

499 

5  %  Paraffin  Oil 
adulteration  

518 

Si7 

494 

COO 

497 

10%  Paraffin  Oil 
adulteration  . 

5*3       5*4 
a< 

489 
AQ2 

491 

488 

4.O2 

490 

Sp.  Gr.  at  60°  F. 

Set  i  Set  2  Set  3 

0.9416       0.9409 


0.9348      0.9350 
0.9330      0.9323 


0.9391 
0.9381 
0.9326 
0.9310 


Sample 

Pure  ................................  0.9423 

5  %  Soya  Bean  Oil  Adulteration  .......  0.9417      0.9407 

10%     "                                            .......  0.9410      0.9401 

5%  Paraffin  Oil 
10%        "        "  " 

Iodine  values  were  also  made  in  the  samples,  with  the  following 
results: 

Sample  Set  i            Set  2            Set  3 

Pure  .................................  160.4        158.8        150.5 

5  %  Soya  Bean  Oil  Adulteration  ........  158.0         155.4         147.8 

10%     "        "      "              "           ........  156.2        151.9         141.6 

5%  Paraffin  Oil                "          ........  155.2         150.8        140.5 

10%        "  143-9         143-4         136-8 
The  impurities  make  quite  an  appreciable  lowering  in  the  iodine 
values." 


STANDARD  SPECIFICATIONS  FOR  PURITY  OF  RAW  CHINESE  WOOD  OiL1 

Properties  and  Tests 
i.   Raw  Chinese  wood  oil  shall  conform  to  the  following  require- 


ments 


1  Amer.  Soc.  Test.  Materials  1915,  423. 


CHINESE  WOOD  OIL  191 

Max.        Min. 

Specific  Gravity  — '—  C 0.943    0.939 

15-5 

Acid  Number 6 

Saponification  Number 195        190 

Unsaponifiable,  per  cent 0.75 

Refractive  Index  at  25°  C 1.520     1.515 

Iodine  Number  (Hiibl  18  hrs.) 165 

Heating  Test  (Browne's  Method),  minutes  . .  12 

Iodine  Jelly  Test,  minutes 4 


CHAPTER  XIV 
SOYA  BEAN  OiL1 

FROM  1890  to  1909  the  price  of  linseed  oil  fluctuated 
between  30  cents  and  50  cents  per  gallon.  On  a  few 
occasions  the  prices  were  higher,  but  a  fair  average  for 
the  19  years  was  40  cents  per  gallon,  although  in  1896 
it  went  as  low  as  25  cents.  Toward  the  end  of  1909  it 
rose  from  60  cents  to  68  cents  within  two  months, 
and  in  September,  1910,  it  reached  $1.01  per  gallon. 
After  that  it  fluctuated  between  that  price  and  75  cents. 
Owing  to  the  high  price  of  linseed  oil  in  1910  many 
painting  operations  were  deferred  awaiting  a  lower  price, 
or  inferior  material  was  used  in  place  of  linseed  oil. 

The  value  of  menhaden  fish  oil  had  already  been 
recognized,  and  while  it  is  admitted  that  fish  oil  replaces 
linseed  oil  for  many  purposes,  it  is  by  no  means  a  true 
substitute.  The  principal  use,  however,  for  fish  oil  to- 
day is  in  the  manufacture  of  linoleum,  printing  inks,  and 
certain  paints  which  are  exposed  either  to  the  hot  sun 
or  on  hot  surfaces. 

In  1909  soya  bean  oil  as  a  paint  oil  was  practically 
unknown.  Since  that  time  many  investigators  have 
published  more  or  less  conflicting  articles  concerning 
soya  bean  oil,  in  which  even  the  physical  and  chemical 
constants  of  soya  bean  oil  varied  to  some  extent.  Owing 
to  the  fact  that  discordant  results  were  continually  ob- 
tained, it  is  only  within  the  past  few  years  that  it  has 

1  Journal  of  Society  of  Chemical  Industry,  June  29,  1912,  No.  12,  Vol. 
XXXI,  by  Maximilian  Toch. 

192 


SOYA    BEAN  OIL  193 

been  possible  to  state  with  some  degree  of  certainty 
whether  soya  bean  oil  is  a  substitute  for  linseed  oil,  an 
adjunct  to  it,  or  neither.  The  reason  for  this  uncertainty 
and  discrepancy  is  apparent  when  it  is  stated  that  the 
author  himself  has  experimented  with  33  different  varie- 
ties of  soya  beans,  while  in  the  records  of  the  Department 
of  Agriculture  at  Washington  no  less  than  280  varieties 
of  soya  beans  are  listed. 

From  time  immemorial  the  soya  bean  has  been 
grown  in  China  and  Japan,  where  it  has  served  as  one  of 
the  staple  articles  of  food  and  as  the  basis  for  a  number 
of  food  preparations.  In  Europe  and  the  United  States, 
however,  the  value  and  uses  of  the  bean  have  been  but 
little  appreciated  until  very  recently  (1908),  when,  on 
account  of  the  scarcity  in  the  cotton  seed  supply  of  the 
world,  soap  and  glycerin  manufacturers  began  to  turn 
their  attention  to  its  possibilities.  In  Manchuria,  where 
by  far  the  major  portion  of  soya  beans  are  grown, 
practically  the  entire  crop  is  available  for  export.  The 
following  figures  taken  from  the  Consular  Reports  will 
serve  to  show  the  extent  of  the  soya  bean  industry  during 
recent  years: 


IQIO 

Tons.  Tons.  Tons. 
Total  shipments  of  beans  from 

Far  East  .................     1,470,870  1,200,000  1,500,000 

Imported  into  Europe  .........        400,000  500,000  340,000 

As  the  above  statistics  indicate,  China  and  Japan 
retain  for  domestic  consumption  practically  two-thirds 
of  the  available  supply  of  beans.  The  sugar  plantations 
in  Southern  China  and  the  rice  fields  of  Japan  annually 
consume  enormous  quantities  of  soya  beans  and  bean 
cake  as  fertilizer,  while  the  extracted  oil  is  used  as  food 
by  the  natives. 


IQ4  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

In  connection  with  the  use  of  soya  beans  and  soya 
bean  oil  for  edible  purposes,  it  may  be  mentioned  that 
there  has  been  recently  established  at  Les  Valees,  France, 
a  thoroughly  up-to-date  factory  for  the  production  of  a 
wide  assortment  of  food  products  from  soya  beans. 
Among  the  more  important  of  these  may  be  mentioned: 
milk,  cheese,  casein,  oil,  jellies,  flour,  bread,  biscuits, 
cakes  and  sauces.  According  to  Dr.  G.  Brooke,  Port 
Health  Officer  of  Singapore,  the  soya  bean,  more  nearly 
than  any  other  known  animal  or  vegetable  food,  contains 
all  the  essential  and  properly  proportioned  ingredients  of 
a  perfect  diet. 

All  soya  beans  are  leguminous  plants,  which  do  not 
tend  to  deplete  the  soil  of  nitrogen,  for  the  typical  soya 
bean  plant  is  self-nitrifying  and  grows  in  almost  any 
soil  that  contains  a  reasonable  amount  of  potash.  In 
addition  to  this,  the  soya  bean  enriches  even  very  poor 
ground  when  used  as  a  ground  manure.  This  is  done  by 
planting  the  seed  promiscuously,  allowing  it  to  grow  to  a 
height  of  about  6  inches,  and  then  turning  it  in.  In  this 
way  both  nitrogen  and  potash  are  given  to  the  soil  for 
future  use  in  an  available  form.  The  average  height  of 
the  soya  bean  plant  is  about  36  inches.  The  pods 
resemble  those  of  our  sweet  pea.  They  are  about  i\ 
inches  in  length  and  are  covered  with  a  hairy  growth. 
Generally  there  are  two  or  three  beans  in  each  pod. 
After  the  oil  is  extracted  from  the  bean  the  cake 
appears  to  be  very  valuable  as  a  cattle  food,  while  the 
leaves  and  stalks,  if  collected  and  set  in  a  dry  place, 
make  excellent  silage.  We  thus  have  practically  the 
entire  plant  available  for  use,  with  the  exception  of  the 
roots. 

The  average  composition  of  the  soya  bean  varies  with- 
in fairly  narrow  limits  among  the  different  varieties 


SOYA    BEAN  OIL 


195 


of   soya   beans.     In   the   following   table   are   listed   the 
analyses  of  a  few  of  the  varieties  of  soya  beans:1 


Nitro- 

Variety 

Water 

Protein 

Fat 

gen  free 

Fibre 

Ash 

. 

extract 

Austin  

8.67 

36.59 

20.  S  5 

24.41 

4.00 

« 

Ito  San  

7.42 

34.66 

19.19 

27.61 

5.97 

Kingston  

7-21? 

36.24 

18.96 

26.28 

4-79 

6.28 

Mammoth  .... 

7-49 

32-99 

21.03 

20.36 

4.12 

5.01 

Guelph     

7-43 

33.96 

22.72 

25-47 

4-57 

15.8=5 

Med.  Yellow.  . 

8.00 

35-54 

19.78 

26.30 

4-53 

5-85 

Samarow   .... 

7.43 

37.82 

20.23 

23.  6s 

15.0=5 

5.82 

When  the  author  obtained  discordant  results  from 
the  soya  bean  oil  then  on  the  market,  the  first  impression 
was  that  the  oil  might  have  been  adulterated,  but  this 
did  not  prove  to  be  the  case.  The  oil  was,  in  all  cases, 
pure  soya  bean  oil,  but  from  a  seed  which  was  not  par- 
ticularly adapted  for  making  a  paint  oil.  Through  the 
U.  S.  Department  of  Agriculture  many  varieties  of  seeds 
were  received,  and  through  the  various  seed  dealers  in 
the  United  States  quantities  of  seeds  of  all  kinds  were 
purchased.  The  method  of  extraction  followed  was  to 
grind  the  seeds  very  finely  in  a  mill  and  digest  with  gaso- 
line in  the  cold.  The  solvent  was  then  evaporated  and 
the  oil  recovered.  Without  going  into  any  lengthy  de- 
tails, the  percentage  of  oil  extracted  averaged  18  per  cent, 
and  although  soya  beans  range  in  color  from  a  cream 
white  to  a  jet  black  it  must  be  noted  here  that  all  the 
oils  extracted  from  the  various  seeds  were  paler  than 
finely  pressed  linseed  oil,  and  none  of  them  showed  the 

1  U.  S.  Dept.  of  Agric.  Bulletin  of  the  Bureau  of  Plant  Industry. 


196  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

chlorophyll  extract  as  markedly  as  fresh  flaxseed.  On 
obtaining  the  various  samples  of  oil  it  became  evident 
why  the  discordant  results  were  obtained,  for  some  of 
them  dried  within  a  reasonable  time  and  some  did 
not. 

It  has  been  stated  that  soya  bean  oil  is  not  as  pale 
as  raw  linseed  oil  and  belongs  to  the  semi-drying  class 
of  oils.  I  must  correct  this  statement;  soya  bean  oils 
made  from  cold  pressed  seeds  such  as  Haberlandt,  Austin, 
Habaro,  Ebony,  Meyer,  and  Ito  San  give  excellent  results. 
They  have  a  specific  gravity  as  high  as  0.926,  with  a  yield 
ranging  from  16  to  19  per  cent.  Furthermore,  a  drier 
made  from  red  lead  or  litharge  is  unsuited  for  soya  bean 
oil,  but  a  tungate  drier,  which  is  a  mixture  of  a  fused 
and  a  precipitated  lead  and  manganese  salt  of  China  wood 
oil  and  rosin,  acts  on  soya  bean  oil  exactly  the  same  as  a 
lead  and  manganese  drier  acts  on  linseed  oil.  In  other 
words,  a  fairly  hard,  resistant  and  perfectly  dry  film 
is  obtained  within  24  hours  by  the  addition  of  from 
5  to  7  per  cent  of  this  drier. 

Soya  bean  oil,  and  when  I  mention  this  name  here- 
after, I  refer  only  to  that  suitable  for  paint  purposes, 
is  the  nearest  oil  we  have  to  linseed,  and  under 
the  proper  impetus  of  the  Department  of  Agricul- 
ture much  of  our  waste  and  unproductive  land 
between  Maryland  and  Georgia,  and  from  the  Coast 
to  the  Mississippi,  will  yield  productive  and  profitable 
crops.  The  only  drawback  to  the  planting  of  soya 
bean  is  the  fact  that  it  needs  much  water.  In  1911 
many  of  the  experimental  plantings  failed  on  account 
of  the  drought  which  was  prevalent  in  the  United 
States,  but  in  low  marsh  land  this  plant  ought  to  yield 
a  profitable  crop.  It  is  doubtful  whether  the  soya  bean 
would  grow  profitably  in  the  extreme  South.  In  Cuba 


SOr.4    BEAN  OIL  197 

the  cow-pea,  which  is  analogous  to  the  soya  bean,  will 
sometimes  grow  to  a  height  of  20  feet,  and  form  a  thick 
mat  around  the  base  or  abutment  of  a  railroad  bridge, 
and  that  within  a  few  months.  This  would  indicate  that 
a  soil  would  have  to  be  selected  where  the  bean  would 
not  grow  to  a  height  greater  than  5  feet,  otherwise  the 
stalks  would  be  too  thick  and  it  would  be  difficult  to 
harvest  it.  Farmers'  Bulletin  No.  372  of  the  Department 
of  Agriculture  makes  the  statement  that  20  Ibs.  of  seeds 
are  required  to  the  acre,  and  that  the  production  is  from 
25  to  40  bushels,  each  bushel  weighing  40  Ibs.  If  this  is 
a  fact,  and  since  little  or  no  fertilizer  is  needed,  and 
when  fertilizer  is  needed  a  preliminary  crop  can  be  grown 
and  turned  in  to  form  its  own  fertilizer,  the  American 
farmer  should  be  encouraged  to  try  this  crop.  Fur- 
thermore, in  Kentucky  two  crops  during  the  summer  can 
be  grown,  for  some  of  the  soya  beans  that  have  been 
tried  there  have  ripened  early,  and  the  second  crop  has 
ripened  late,  two  different  selections  of  seed  having  been 
used.  The  statement  has  been  made  that  soya  bean 
could  not  be  harvested  properly  in  this  country  on 
account  of  the  high  cost  of  labor  as  compared  with  that 
of  Manchuria  and  Japan,  but  this  is  evidently  erroneous, 
in  view  of  the  fact  that  enormous  quantities  of  beans  are 
grown  in  Minnesota  for  food  purposes  and  harvested 
by  machinery.  Even  in  Manchuria  the  beans  are  allowed 
to  dry  and  then  thrashed  out  by  means  of  horse  power. 
At  any  rate,  if  we  have  any  difficulties  now  with  the 
harvesting  of  a  new  kind  of  crop,  it  is  safe  to  assume  that 
with  the  American  inventive  genius  in  harvesting  ma- 
chinery, appliances  will  be  invented  which  will  overcome 
this,  for  the  soya  business  has  no  greater  harvesting 
difficulties  than  the  edible  bean. 

Soya  bean  oil  appears  to  consist  of  from  94  to  95 


198 


CHEMISTRY  AND    TECHNOLOGY  OF  PAINTS 


per  cent  of  glycerol  esters.1  Of  these  15  per  cent  are 
saturated  acids  such  as  palmitic  acid,  and  80  per  cent  are 
liquid  unsaturated  fatty  acids  containing  70  per  cent 
oleic  acid,  24  per  cent  linolic  acid,  and  6  per  cent  linolenic 
acid.  The  iodine  number  of  soya  bean  oil  has  been 
given  as  ranging  from  121  to  124,  but  the  Manchurian 
cold  pressed  oil  will  average  as  high  as  133. 

It  may  be  of  interest  to  show  a  comparative  table 
here  between  the  physical  and  chemical  constants2  of 
soya  bean  oil  of  known  origin  like  Manchurian  cold 
pressed  oil  as  compared  with  linseed  oil. 

SOYA  BEAN  OIL 


Name 

Color 
of  seed 

Color  of 
oil 

Sp.  gr. 

15°  c 

Acid 
value 

Iodine 
value 

Meyer  

Brown 

^ 

0.9264 

0.44 

127.0 

Peking   

Black 

0.9279 

0.14 

1^.4 

Haberlandt.  .  i 

Straw- 
yellow 

extremely 
pale 

s        1   .7 

0.9234 

O.OO 

•J  tJ      * 

129.8 

Farnham.  .  .  .  j 

Straw- 
yellow 

0.9234 

0.65 

131.8 

Black, 

Taha  • 

olive 
saddle 

pale  amber 

0.9248 

0.16 

127.0 

somewhat 

Mammoth.  .  .  ' 

Straw- 
yellow 

deeper  than 
above 

0.9222 

0.47 

118.2 

Brown 

0.9248 

0.17 

129.3 

Edward  \ 

Straw- 

i 

!•  med.  amber 

0.9257 

1.14 

124.6 

yellow 

J 

f  same  depth 

Shanghai.  .  .  . 

Black 

•j  as  previous, 

0.9241 

0.63 

127.8 

i  olive  tone 

Refined  linseed  oil  .... 

0-933 

I.O 

1  80.  1 

1  H.  Matthias  and  H.  Dahle  —  Arch.  Pharm.,  1911,  294,  424-435- 

2  Results  obtained  in  the  research  laboratory  of  Toch  Brothers. 


SOYA   BEAN  OIL  199 

The  specific  gravity  determinations  were  made  with 
the  pyknometer.  The  iodine  values  were  obtained  in 
accordance  with  Hubl's  method.  The  iodine  values 
indicated  are  somewhat  lower  than  those  of  cold  pressed 
Manchurian  bean  oil.  This  is  no  doubt  to  be  ascribed 
to  the  circumstance  that  the  solvent  with  which  the  oil 
was  extracted  was  driven  off  by  evaporation  in  open 
vessels  on  the  water  bath,  so  that  the  oil  became  slightly 
oxidized. 

Soya  bean  oil  which  is  suitable  for  paint  purposes  has 
two  characteristics  which  enable  the  chemist  to  deter- 
mine whether  this  oil  is  suitable  or  not.  In  the  first 
place,  soya  bean  oil  when  heated  up  to  500°  F.  for  a  few 
minutes  will  bleach  and  remain  bleached.  Some  sam- 
ples which  the  author  has  examined  have  turned  almost 
water  white.  Linseed  oil  has  this  characteristic,  but  not 
to  the  same  degree.  Cold  pressed  soya  bean  oil  made 
from  the  samples  indicated  in  the  previous  table,  when 
heated  to  500°  F.,  and  blown  with  dry  air  for  from  5  to  7 
hours,  thickens  exactly  the  same  as  linseed  oil,  and 
attains  a  gravity  of  0.960  or  over.  This  is  the  surest 
indication  that  the  soya  bean  oil  which  will  thicken 
under  these  conditions  and  remain  pale  is  suitable  for 
paint  purposes.  This  thickened  oil  has  excellent  qualities 
and  advantages  for  making  what  we  call  in  this  country 
"baking  japans,"  and  what  are  known  in  England  as 
"stoving  varnishes." 

A  sample  of  standard  cold  pressed  Manchurian  bean 
oil  was  heated  to  500°  F.,  and  blown  vigorously  for  7 
hours  after  cooling  to  300°  F.  The  following  results  were 
obtained : 


2OO 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


Sp.  gr. 
60°  F. 

Acid 
value 

Iodine 
value  (.Wij's.) 

Original  oil.  .  .  . 

O.O2Q 

2  6 

1  11  6 

Blown  oil  

O.Q63 

I.O 

iOO'u 
IOC  T. 

It  is  interesting  to  note  that  the  acid  value  was 
reduced  by  blowing.  The  blown  oil  dried  in  3!  days, 
whereas  the  original  sample  required  from  5  to  6 
days. 

It  appears  that  the  varnish  made  from  a  suitable 
soya  bean  oil  bakes  very  hard  and  retains  an  abnormal 
flexibility.  -,As  regards  the  wearing  quality  of  pure  soya 
bean  oil  compared  with  pure  linseed  oil  for  paint,  the 
author  has  had  somewhat  less  than  three  years'  experi- 
ence, and  can  only  say  that  it  is  not  quite  as  good  as 
that  of  linseed  oil.  A  2-year  exposure  on  a  loo-foot 
fence  gave  slightly  better  results  for  the  linseed  oil  as  to 
hardness  and  less  gloss  for  the  soya  bean  oil,  but  a 
mixture  of  half  soya  bean  and  half  linseed  oil  showed 
approximately  the  same  results,  while  a  varnish  made  of 
25  per  cent  of  China  wood  oil  with  75  per  cent  soya 
bean  oil  gave  equally  hard  results  as  linseed  oil.  It  is 
too  soon  to  prognosticate  the  value  of  soya  bean  oil  for 
exterior  painting,  but  for  interior  painting  soya  bean  oil 
is  the  equal  in  every  respect  of  linseed  oil,  and  particularly 
when  treated  with  a  tungate  drier. 

Cobalt  drier  will,  under  many  circumstances,  dry  even 
those  soya  bean  oils  which  are  not  suited  for  paint  pur- 
poses, but  for  the  present  cobalt  drier  is  rather  too  expen- 
sive. It  has  been  stated  that  from  i  to  i|  per  cent 
cobalt  drier  will  dry  soya  bean  oil  and  fish  oil.  This  is 


SOYA   BEAN  OIL  201 

practically  true,  but  i\  per  cent  is  really  needed  to  get 
the  proper  drying  within  24  hours.  Cobalt  Tox 
Tungate1  is  probably  the  ideal  drier  for  soya  bean  and 
fish  oils.  This  drier,  when  present  in  soya  bean  oil 
to  the  extent  of  from  5  to  7  per  cent,  will  dry  the 
latter  within  12  hours. 

It  is,  of  course,  possible  to  determine  and  differ- 
entiate a  mixture  of  raw  soya  bean  oil  and  raw  linseed 
oil,  for  the  iodine  values  and  specific  gravities  are  good 
indications,  but  when  25  per  cent  of  soya  bean  oil  is 
added  to  a  mixed  paint  neither  the  author  nor  any- 
one in  his  laboratory  can,  in  all  instances,  detect  its 
presence. 

Blown  and  thickened  soya  bean  oil  is  already  used 
by  a  number  of  the  linoleum  and  table  oilcloth  manu- 
facturers, and  for  printing  ink  purposes  it  presents  some 
advantages.  For  the  manufacture  of  enamel  paints 
heavy  bodied  soya  bean  oil  produces  most  beautiful  re- 
sults, and  as  perhaps  95  per  cent  of  all  enamel  paints  are 
used  for  interior  decorative  or  protective  purposes  in 
this  country  its  use  should  be  encouraged. 

It  is  not  within  the  province  of  the  writer  to  forecast 
the  future  of  any  paint  oil,  but  there  is  no  doubt  that  if 
a  campaign  of  education  be  urged  among  the  farmers, 
particularly  in  those  states  where  soil  has  been  regarded 
as  unproductive,  and  the  proper  selected  seeds  of  soya 
beans  are  planted,  no  scarcity  in  the  flaxseed  crop  will 
ever  again  be  a  menace  to  the  paint  and  varnish  indus- 
tries. At  the  time  of  writing  linseed  oil  is  quoted  at  75 
cents  per  gallon  and  soya  bean  oil  at  55  cents  per  gallon. 
As  soon  as  thousands  of  acres  shall  have  been  planted 

1  So  called  because  it  was  first  prepared  by  the  author.  It  is  a 
cobaltic  salt  of  China  wood  oil.  Unless  the  cobalt  is  trivalent,  it 
will  not  act  as  a  drier. 


202  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

with  soya  beans,  the  proper  machinery  installed,  and  the 
sale  for  the  cake  and  the  silage  arranged,  soya  bean  oil 
will  sell  at  from  25  to  35  cents  per  gallon,  and  after  the 
ground  has  been  productive  of  soya  beans  for  some  time 
it  will  be  fit  for  the  growing  of  even  the  most  difficult 
crops. 


CHAPTER   XV 

FISH  OIL 

WE  are  all  prone  to  call  all  oils  of  a  fishy  nature  "fish 
oils,"  and  the  author  desires  to  differentiate  between  the 
real  fish  oils  and  the  pseudo  fish  oils,  for  there  are  several 
marine  animal  oils  which  have  fishy  characteristics  but 
which  are  not  strictly  fish  oils,  and  which  do  not  serve  as 
good  a  purpose  as  those  which  are  strictly  extracted  from 
fishes.  Some  of  the  fish  oils — like  cod  liver  oil —  even  if 
they  were  cheap  enough,  are  not  totally  adapted  for 
paint  use.  The  animal  oils  which  have  always  been 
regarded  as  fish  oils,  but  which  the  author  calls  pseudo 
fish  oils,  and  that  are  in  the  market  and  easily  pur- 
chased at  a  reasonable  price,  are  whale  oil,  porpoise  oil 
and  seal  oil.  All  of  these  oils  are  by  no  means  drying 
oils,  and  even  if  they  are  admixed  with  drying  oils  like 
tung  oil  and  boiled  linseed  oil,  and  an  additional  amount 
of  drier  added,  they  are  peculiarly  hygroscopic,  and  after 
three  months,  although  these  oils  may  be  apparently 
dry,  they  become  sticky  when  the  humidity  rises  above 
So. 

The  following  figures  represent  some  constants  of 
fish  oils,  the  specific  gravity  and  the  iodine  number 
being  given  in  each  case.  The  iodine  number  is  a  char- 
acteristic indication  of  the  value  of  a  fish  oil  for  paint 
purposes. 


203 


204  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


FISH  OIL  CONSTANTS 

Specific       Iodine  No. 
Gravity       Hiibl, 
20°  C  4  hours 

No.  i  crude  whale  oil °-9I95  I36.i 

No.  i  filtered  whale  oil 0.9168  125.0 

No.  2  filtered  whale  oil 0.9187  142.9 

Cod  oil 0.9196  147-3 

Porpoise  body  oil 0.9233  132.3 

Seal  oil  —  water  white 0.9227  143.0 

Menhaden  Oil 

Extra  bleached  winter °-9237  150.4 

Bleached  —  refined °-9273  161.2 

Regular 0.9249  165.7 

Dark  brown 0.9250  154-5 

The  specific  gravities  were  determined  with  the  aid 
of  the  Westphal  balance. 

The  iodine  numbers  were  determined  according  to  the 
standard  method  of  Hiibl. 

The  fish  oil  used  for  paint  purposes  is  the  variety 
obtained  from  the  Menhaden  fish,  and  the  winter  bleached 
is  the  variety  to  be  recommended.  When  refined  by 
the  simple  process  of  filtering  through  infusorial  earth 
and  charcoal  its  color  is  that  of  refined  linseed  oil,  with 
little  or  no  fishy  odor;  in  fact,  in  the  purchasing  of  fish 
oil  for  paint  purposes  it  is  well  to  beware  of  a  fish  oil 
that  has  the  so-called  characteristic  "fishy"  odor.  In 
its  chemical  properties  it  is  so  similar  to  linseed  oil  that 
it  is  difficult  to  differentiate  between  them.  It  must 
be  observed  that  oils  in  mixed  paints  are  not  presented 
to  the  chemist  or  practical  man  in  their  raw  or  natural 
state,  but  they  have  been  boiled  with  driers  and  ground 
with  pigments  so  that  their  characteristics  are  entirely 


FISH  OIL  205 

altered.  The  old-time  painter  when  he  condemned  a 
mixed  paint  would  smell  it,  taste  it,  rub  it  between  his 
thumb  and  forefinger,  smell  it  again,  look  wise,  and  say 
despairingly,  "fish  oil."  As  a  matter  of  fact,  the  adul- 
teration of  paints  was  seldom,  if  ever,  caused  by  the 
addition  of  fish  oil,  for  the  reason  that  the  price  of  a 
good  fish  oil  always  approximated  that  of  a  raw  linseed 
oil,  and  there  were  so  many  other  cheaper  paraffin  oils 
to  be  had  that  the  occurrence  of  fish  oil  in  a  mixed 
paint  was  relatively  rare.  The  specific  gravities  of  fish 
oils  freshly  made  and  containing  no  admixture  of  other 
species,  but  representing  the  pressing  of  only  one  species, 
are  as  a  general  rule  below  .927.  Its  iodine  number  is 
so  close  to  that  of  linseed  oil  that  in  its  raw  state,  except- 
ing for  its  characteristic  odor  and  the  Maumene  test,  it 
is  rather  difficult  to  differentiate  these  oils  with  cer- 
tainty. The  author  is  inclined  to  believe  that  this 
characteristic  odor  is  due  to  phosphorous  decomposition 
compounds.  If  a  linseed  oil  be  heated  to  500°  F.,  mixed 
with  Japanners  Prussian  brown  or  Prussian  blue,  it  de- 
velops acrolein,  which  is  identical  in  odor  with  that  from 
the  fish  oil.  When  Menhaden  oil  is  treated  with  8  ounces 
of  litharge  to  the  gallon  and  kept  at  a  temperature  of  400° 
to  500°  F.,  for  ten  hours,  it  thickens  perceptibly  and  can 
be  reduced  proportionately  with  naphtha,  but  the  amount 
of  loss  by  this  treatment  with  litharge  makes  it  very 
expensive  in  the  end. 

The  results  obtained  from  the  proper  grades  of  fish 
oil  warrant  the  use  of  fish  oil  in  the  hands  of  an  intelli- 
gent manufacturer,  and  if  used  up  to  75  per  cent  pro- 
duces excellent  results  for  exterior  purposes.  For  interior 
purposes  fish  oil  does  not  seem  to  be  desirable,  for  it 
gives  off  noxious  gases  for  a  long  time.  When  fish  oil 
is  mixed  with  linseed  oil  even  up  to  75  per  cent  it 


206  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

gives  excellent  and  lasting  results  and  does  not  show 
any  hygroscopic  properties,  but  when  used  in  the  raw 
state,  particularly  in  conjunction  with  pigments  which  in 
themselves  are  not  catalytic  driers,  the  results  are  not 
satisfactory. 

For  some  years  some  of  the  enamel  leather  and  print- 
ing ink  manufacturers  have  adopted  the  use  of  fish  oil 
as  a  medium  to  replace  linseed  oil  with  excellent  results, 
and  the  enamel  leather  which  is  produced,  while  not  so 
high  in  gloss  as  that  made  entirely  of  linseed  oil,  is  much 
more  flexible  and  possesses  an  unctuousness  which  pre- 
vents it  from  cracking.  But  fish  oil  for  leather  purposes 
shows  a  peculiar  defect,  and  a  campaign  of  education 
will  be  necessary  if  ever  this  material  is  to  be  used  for 
the  manufacture  of  shoes  or  auto  tops,  for  fish  oil,  par- 
ticularly when  it  originally  has  a  high  acid  number,  seems 
to  effloresce  and  give  an  undesirable  bloom  to  enamel 
leather,  which,  however,  can  be  removed  from  the  sur- 
face by  the  ordinary  application  of  either  benzine  or  a 
mixture  of  benzine  and  turpentine.  At  the  same  time, 
enamel  leather  is  very  largely  used  for  carriage  and 
automobile  tops,  and  for  shoes,  and  wherever  it  is  used 
for  these  purposes  these  products  are  continually  polished. 

Menhaden  oil  is  the  only  oil,  with  the  possible  excep- 
tion of  China  wood  oil,  which  can  be  used  for  making 
smoke-stack  paints  that  will  withstand  the  action  of 
excessive  heat  and  light.  When  treated  as  described,  its 
intrinsic  value  is  far  beyond  that  of  linseed  oil,  and  a 
smoke-stack  paint  made  in  this  manner  sells  for  one-third 
more  than  a  linseed  oil  paint.  It  is  impossible,  however, 
to  treat  Menhaden  oil  for  this  purpose,  except  at  an 
excessive  cost,  because  the  acrolein  developed  nauseates 
the  workmen,  the  loss  in  evaporation  is  very  large,  and 
the  treatment  with  litharge  is  such  that  the  oil  must 


FISH  OIL  207 

be  thinned  before  it  has  an  opportunity  to  compound  or 
semi-solidify.  In  its  raw  state,  after  treatment  with 
animal  charcoal  and  infusorial  earth,  it  is  used  to  some 
extent  with  a  heavy  boiled  linseed  oil  for  making  water- 
proof roof  paints,  for  painting  canvas,  freight  cars,  ship 
decks,  etc.  When  mixed  with  linseed  oil  up  to  about 
25  per  cent  it  is  extremely  difficult  to  determine  the 
amount  present  by  means  of  its  chemical  constants  or 
characteristics. 

The  following  are  the  constants  of  the  Menhaden  oil 
which  is  generally  used  in  the  United  States  for  making 
heat-resisting  paints: 

CONSTANTS  OF  FISH  OIL 

Specific  Gravity Q-931 

Saponification 190. 

Iodine  Value 150-165 

There  is  a  great  demand  for  baking  japans  which 
shall  be  flexible  and  at  the  same  time  be  so  thoroughly 
baked  that  they  adhere  to  the  surface  most  tenaciously 
and  form  an  excellent  enamel,  and  for  this  purpose  we 
know  that  the  reasonable  use  of  fish  oil  improves  baking 
japans  very  much  indeed. 

We  are  also  aware  that  along  the  seacoast,  where 
paint  disintegrates  very  rapidly  on  account  of  the  sea 
air,  a  fairly  liberal  use  of  properly  treated  fish  oil  serves 
a  useful  purpose. 

WThen  red  lead  is  mixed  33  Ibs.  to  a  gallon  of  linseed 
oil  it  thickens  up  after  a  very  short  time  and  becomes 
unfit  for  use.  A  properly  neutralized  fish  oil  prevents 
the  hardening  or  setting  of  the  red  lead  in  the  package, 
and  a  paste  of  this  material  can  be  transported  a  great 
distance  and  will  last  many  months  in  a  fresh  and  soft 
condition. 


208  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

In  the  tests  made  by  the  author  on  fish  oils  and  lin- 
seed oil  without  the  admixture  of  driers,  it  was  found  that 
the  Menhaden  fish  oil  and  the  linseed  oil  dried  approxi- 
mately the  same,  but  the  seal  oil  and  whale  oil  were 
still  sticky  after  two  weeks.  This  may  be  an  unfair 
test,  for  these  other  oils  can  be  manipulated  with  the 
proper  driers  and  they  will  serve  a  fairly  good  purpose, 
but  inasmuch  as  Menhaden  fish  oil  appears  to  be  satis- 
factory for  this  test  even  without  a  drier  its  superiority 
over  the  animal  oils  is  apparent. 

Menhaden  oil  should,  of  course,  be  used  with  a  drier, 
and  for  that  purpose  the  best  results  are  obtained  by 
means  of  a  tungate  drier.  A  tungate  drier  is  one  in 
which  tung  oil  or  China  wood  oil  is  boiled  with  a  lead 
and  manganese  oxid,  and  when  the  solution  is  complete 
this  is  then  mixed  with  a  properly  made  resinate  of 
lead  and  manganese.  Such  a  drier  becomes  soluble  in 
the  oil  at  temperatures  over  100°  C.,  and  hardens  the 
resulting  paint  very  thoroughly.  For  fabrics,  however, 
fish  oil  must  be  heated  to  a  temperature  of  over  200°  C., 
and  if  air  is  injected  at  such  a  temperature  the  glycerides 
are  expelled  and  thick  oil  is  produced  which,  in  con- 
junction with  the  drier  just  named,  is  equally  good  for 
printing  inks.  It  is  advisable,  however,  to  add  at  least 
25  per  cent  of  either  a  heavy  bodied  linseed  oil  or  a  raw 
linseed  oil  which  does  not  "break"  before  the  manipula- 
tion just  referred  to  is  begun. 

For  stacks,  boiler  fronts,  etc.,  the  treatment  of  fish 
oil  up  to  220°  C.,  with  litharge  makes  a  heat-resisting 
medium  that  is  far  superior  to  anything  excepting  China 
wood  oil,  and  for  both  heat-resisting  and  exposure  to  the 
elements  fish  oil  is  superior  to  China  wood  oil. 

The  following  is  taken  from  the  U.  S.  Navy  Depart- 
ment specifications  for  fish  oil  for  paint  purposes: 


FISH  OIL  209 

Quality 

1.  To  be  strictly  pure  winter-strained,  bleached,  air-blown  Men- 
haden fish  oil,  free  from  adulteration  of  any  kind. 

Chemical  Constants 

2.  The  oil  shall  show  upon  examination: 

Maximum  Minimum 

Specific  gravity °-935     °-93° 

Iodine  number  (Hanus) 165        145 

Acid  number 6 

Physical  Characteristics 

3.  The  oil  when  poured  on  a  glass  plate  and  allowed  to  drain 
and  dry  in  a  vertical  position,  guarded  from  dust  and  exposure  to 
weather,  shall  be  practically  free  from  tack  in  less  than  75  hours  at 
a  temperature  of  70°  F.     When  chilled,  the  oil  shall  flow  at  temper- 
atures as  low  as  32°  F. 


CHAPTER  XVI 

MISCELLANEOUS  OILS 
HERRING  OiL1 

WITHIN  recent  years  the  subject  of  fish  oils  has 
received  considerable  attention,  first  from  the  leather  and 
soap  manufacturers  and  subsequently  from  the  paint 
chemist.  Hitherto  fish  oil  played  the  role  of  a  rather  un- 
important by-product  in  the  course  of  fertilizer  or  "scrap" 
production,  for  which  there  seems  to  have  been  always 
a  large  demand. 

As  the  peculiar  properties  and  industrial  possibili- 
ties of  fish  oils  became  more  thoroughly  appreciated  in 
the  light  of  investigations  carried  out  by  progressive 
manufacturers,  the  fish  oil  industry  received  a  new 
lease  of  life  and  grew  until  it  rivalled  in  importance 
the  fertilizer  industry  to  which  it  had  previously  been 
tributary. 

Of  the  numerous  varieties  of  fish  oils  which  have 
at  one  time  or  another  appeared  upon  the  market,  Men- 
haden oil  alone  seems  to  have  established  itself  on  a  firm 
basis  in  the  manufacture  of  special  kinds  of  heat-resisting 
paints.  Its  application,  therefore,  is  no  longer  an  experi- 
ment; it  is  an  established  fact. 

Latterly,  attention  has  been  more  particularly  directed 
toward  seal,  whale,  cod,  porpoise,  and  herring  oils,  with 

1  By  A.  Lusskin,  8th  Int.  Congress  of  Applied  Chemistry;  written 
in  the  research  laboratory  of  Toch  Brothers  under  the  direction  of 
the  author. 


HERRING  OIL  21 1 

a  view  to  investigating  their  utilizability  in  the  indus- 
tries. Of  these,  seal,  cod  and  porpoise  body  oils  have 
proved  to  be  in  many  ways  as  good  as  Menhaden  oil, 
but  are  beyond  the  reach  of  the  paint  manufacturer  on 
account  of  considerations  of  price. 

Whale  oil,  which  is  now  obtainable  in  the  form  of  a 
clear,  pale  material,  comparatively  free  from  objection- 
able odors,  has  not  as  yet  been  successfully  manipulated 
to  give  very  good  drying  results. 

In  the  treatment  of  fish  oils,  several  considerations 
must  be  constantly  kept  in  mind  in  order  to  obtain  the 
best  results: 

1.  The   oil   must   be   free   from   high   melting   point 
glycerides  or  fatty  acids;  or,  to  use  the  technical  term, 
the  oil  must  be  "winter-pressed."     Most  fish  oils  contain 
a  large  amount  of  saturated  glycerides  of  the  nature  of 
palmitin  which  separate   from   the  oils   on   standing   for 
any  length  of  time  at  a  low  temperature.     When  these 
have  been  removed  from  the  oil,  the  resulting  product  is 
found  to  be  much  more  amenable  to  successful  treatment 
than   it   otherwise   is.     It   would   seem   that   these   high 
melting  point  fats  tend  to  retard  or  to  prevent  the  drying 
of  fish  oils,  giving  films  which  remain  greasy  for  a  very 
long  time. 

2.  Very  frequently,   oils  are   received  which  have   a 
high   content  of  free  fatty   acids.      In   the   case   of   one 
sample  of  herring  oil,  this  was  as  high  as  41.9.     Under 
such  circumstances,  it  is  perfectly  evident  that  the  drying 
of  the  oil  would  be  very  largely  inhibited.     In  addition, 
such  an  oil,  used  as  a  paint  vehicle,  in  conjunction  with 
pigments  like  red  lead,  white   lead,  and  zinc   oxid  will, 
in  a  very  short  space  of  time,  "liver"  up  and  form  the 
lead  and  zinc  soaps  of  the  fatty  acids.     This  was  very 
largely  responsible  for  the  poor  results  obtained  with  the 


212  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

fish  oils  which  were  first  introduced  on  the  market. 
The  free  fatty  acids  are  formed  when  the  oil,  extracted 
from  the  fish  by  boiling  in  water,  is  subjected  to  the 
action  of  the  decomposition  products  from  the  bodies  of 
the  fish  for  a  longer  time  than  is  absolutely  necessary 
to  break  open  the  oil-containing  cells. 

3.  Finally  it  must  be  remembered  that  driers,  which 
serve  very  well  for  vegetable  drying  oils,  will  not,  in 
general,  function  properly,  when  utilized  for  fish  oils. 
The  tungate  driers,  and  particularly  the  cobalt  tungates, 
can  generally  be  depended  upon  in  the  case  of  oils  which 
do  not  yield  to  the  action  of  the  ordinary  linseed  oil 
driers,  provided  however,  the  two  conditions  named  above 
have  been  satisfied. 

The  writer  recently  had  his  attention  called  to  several 
grades  of  herring  oil,  which,  at  first  glance,  appeared 
desirable  from  the  paint  manufacturer's  standpoint. 
Accordingly  an  investigation  was  started  to  test  its 
adaptability  for  paint  purposes,  and  to  compare  its  be- 
havior with  that  of  Menhaden  oil. 

Herring  oil  occurs  in  the  bodies  of  Clupeus  C.  and 
V.  (Japanese  herring  varieties)  and  Clupeus  harengus 
(European  or  North  Sea  herring). 

The  method  of  extracting  the  oil  from  herring  is  the 
one  universally  used  in  the  fish  oil  industry,  viz.,  ex- 
traction in  boiling  water. 

Two  representative  samples  of  herring  oil,  furnished 
by  two  of  the  leading  oil  concerns  in  the  States,  were 
experimented  with  in  conjunction  with  Menhaden  and 
other  fish  oils.  The  following  analytical  constants  were 
obtained: 


HERRING  OIL 


213 


No. 

Color 

Odor 

SP.  Gr. 
15°  C 

Acid 
Value 

Iodine 
Value 

fi  Herring  Oil 

Very  Pale 

Good 

0.9240 

2.4 

J37-9 

jf  2  Herring  Oil 

Dark  Brown 

Bad 

0.9210 

41.9 

136.1 

Blown  Oil  #2 

Deep  Red 

Almost 

0.9654 

25-7 

89.94 

None 

Winter-Pressed  |   // 

r   TF? 

Extremely 

Fair 

0.920 

39-4 

136.1 

Refined 

Pale 

#i  Crude  Whale  Oil 

Very  Pale 

Good 

0.9230 

0.6 

136.1 

#i  Filt.  Whale  Oil 

Very  Pale 

Good 

0.9203 

2-3 

125.0 

#2  Filt.  Whale  Oil 

Pale  Amber 

Very  good 

0.9222 

14-5 

142.9 

Porpoise  Body  Oil 

Very  Pale 

Very  good 

0.9268 

2.8 

132.3 

Menhaden  Oils 

Ext.  Bleached 

Winter  Oil 

Very  Pale 

Fair 

0.9272 

o-5 

l5°-4 

B  leached-Refined 

Pale  Amber 

Not  bad 

0.9308 

5-7 

161.2 

Regular 

Deep  Red 

Bad 

0.9284 

8.4 

165.7 

*  The  part  of  the  table  below  the  asterisk  (with  exception  of  the 
acid  values),  is  from  a  paper  on  Fish  Oils  delivered  by  M.  Toch 
before  the  Amer.  Chem.  Soc.,  Dec.  1911,  and  published  in  the  Journal 
of  Industrial  and  Engineering  Chemistry. 

Crude  herring  oil,  even  though  very  dark  in  color, 
yields  a  very  clear,  pale  product  when  treated  with 
Fuller's  earth  for  a  short  time  at  about  250°  F.,  and  then 
for  some  time  longer,  at  the  temperature  of  boiling 
water.  In  addition  the  odor  is  considerably  improved. 

In  the  case  of  the  crude  herring  oil  listed  above,  the 
sample  was  kept  for  several  hours  at  about  60°  F.  to 
permit  high-melting  fats  to  separate  out.  The  portion 
which  remained  liquid  corresponded  to  a  winter-pressed 
oil.  Since  the  acid  and  iodine  numbers  were  prac- 
tically unchanged  it  seems  that  the  solid  fats  contained 
saturated  and  unsaturated  compounds  in  about  the  same 
proportions  as  the  crude  oil. 


214  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Another  sample  of  the  oil  was  heated  to  320°  F.  and 
blown  with  air  for  about  8  hours.  The  effects  produced 
on  the  constants  are  shown  above.  The  oil  was  very 
heavy  and  viscous  but  had  the  deep  red  color  which  fish 
oils  so  readily  assume.  It  must  be  noted  also  that  the 
"fish"  odor  was  very  faint.  The  reduction  in  acid  value 
would  seem  to  indicate  that  the  oil  contained  fatty  acids 
which  were  volatile  at  the  temperature  of  blowing. 

Attempts  to  dry  the  samples  of  herring  oil  did  not 
prove  successful,  even  when  very  powerful  driers  were 
used.  This  cannot,  however,  be  interpreted  to  mean 
that  herring  oils  are,  in  general,  not  capable  of  drying. 

Porpoise  body  oil  and  Menhaden  oil,  under  similar 
conditions,  dried  satisfactorily. 

The  blown  herring  oil  could  very  well  be  used  for  the 
production  of  smoke-stack  paints  and  for  paints  intended 
to  resist  the  "chalking"  action  of  salt  air.  Herring  oil 
is  at  present  used  to  a  certain  extent  in  leather  manu- 
facture together  with  some  of  the  other  fish  oils  like 
Menhaden  and  whale  oil.  In  regard  to  herring  oil,  as 
with  many  of  the  other  materials  which  are  being  intro- 
duced from  time  to  time,  the  final  word  cannot  be  spoken 
until  many  more  specimens  have  been  examined  and 
given  a  fair  test. 

CORN  OIL 

Corn  oil  is  made  in  very  large  quantities  in  the 
United  States,  and  is  of  considerable  value  as  a  paint 
material.  It  is  seldom  so  much  cheaper  than  linseed  oil 
or  China  wood  oil  that  it  is  used  as  an  adulterant  for 
these  oils;  in  fact,  many  manufacturers  would  probably 
use  it  irrespective  of  the  price  up  to  about  10  per  cent 
in  certain  classes  of  mixed  paints  in  order  to  prevent 
hardening  or  settling.  A  large  number  of  paint  manu- 


CORN  OIL  215 

facturers  in  the  United  States  who  grind  heavy  paste 
paints,  such  as  Venetian  reds,  ochres  and  white  paints 
containing  large  amounts  of  barytes,  frequently  use  from 
10  to  70  per  cent  of  corn  oil,  not  because  it  is  any 
cheaper  than  linseed  oil,  but  for  the  reason  that  the 
resulting  mass  never  becomes  hard  in  the  package  as  it 
does  where  pure  linseed  oil  is  used. 

Corn  oil  has  a  great  analogy  to  soya  bean  oil,  with  the 
one  exception  that  corn  oil  is  not  as  pale  nor  can  it  be 
bleached  as  pale  as  soya  bean  oil,  and  when  it  is  bleached 
by  chemical  means  it  dries  very  badly. 

Corn  oil  is  known  in  England  as  maize  oil.  Paint 
manufacturers  in  England  appear  to  have  very  little 
knowledge  of  this  oil  and  regard  it  as  a  non-drying  oil, 
and  yet  corn  oil  is  even  more  than  a  semi-drying  oil, 
particularly  when  heated  with  strong  drying  oils  like 
China  wood  oil  and  cobalt  and  manganese  drier.  In 
the  textile  arts,  such  as  the  manufacture  of  linoleum  and 
table  oilcloth,  where  flexibility  is  desired,  large  quantities 
of  corn  oil  are  from  time  to  time  used  with  excellent 
results.  When  an  oil  like  corn  oil  is  used  for  paint 
purposes  in  limited  quantities  its  characteristic  of  slow 
drying  or  tacky  drying  is  eliminated  if  it  is  properly  ma- 
nipulated. Corn  oil  will  take  up  the  lead  and  manganese 
salts  just  the  same  as  linseed,  but  in  conjunction  with 
linseed  oil.  It  can  be  blown  and  can  be  thickened  by 
heat,  and  being  very  flexible  it  has  a  distinct  advantage. 
It  has  been  stated,  although  the  author  has  not  tried  this, 
that  for  priming  new  wood  half  corn  oil  and  half  linseed 
oil  with  sufficient  drier  and  volatile  solvent  produce  a 
priming  coat  to  which  a  second  coat  of  linseed  oil  paint 
will  adhere  perfectly. 

The  physical  and  chemical  constants  of  corn  oil 
cannot  be  given  exactly  for  the  reason  that  samples  vary. 


2l6  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Its  specific  gravity  will  run  from  0.920  to  0.926;  its 
saponification  value  will  average  190;  and  its  iodine 
value  will  average  120,  although  several  samples  exam- 
ined by  the  author  have  shown  as  high  an  iodine  value 
as  130. 


CHAPTER  XVII 

TURPENTINE 

TURPENTINE  occupies  the  same  relative  position  among 
the  vehicles  of  paints  and  varnishes  as  white  lead  does 
among  the  pigments.  It  is  impossible  to  say  for  how 
many  generations  turpentine  was  the  only  solvent  or 
diluent  known  to  the  paint  and  varnish  industry,  and 
therefore  when  other  solvents  were  introduced  they  were 
looked  upon  as  adulterants. 

The  methods  used  in  the  manufacture  of  turpentine 
are  very  well  known;  the  sap  of  the  Georgia  pine  and 
two  or  three  other  species  of  pine  trees  growing  in 
the  southern  part  of  the  United  States  is  collected 
and  distilled  with  steam.  The  distillate  is  known  as 
turpentine,  and  that  which  remains  behind  in  the  still 
is  known  as  rosin  (colophony).  American  turpentine 
has  a  very  pleasant  odor,  and  from  several  combus- 
tion analyses  made  by  the  author,  the  composition 
of  turpentine  taken  directly  from  the  barrel  as  shipped 
from  the  South  corresponds  absolutely  with  the  theo- 
retical formula  d0Hi6.  It  has  absolutely  none  of  the 
qualities  of  a  paint  preservative,  but  is  used  only  to 
increase  the  spreading  power  and  working  quality  of 
paint.  Entirely  too  much  stress  is  laid  upon  the  value  of 
turpentine  as  a  paint  vehicle,  and  the  sooner  the  chem- 
ist and  the  consumer  realize  that  turpentine  is  simply 
an  auxiliary,  the  sooner  will  better  substitutes  be  used. 

If  the  forestry  department  of  this  government  will  not 
interfere  with  the  destruction  of  the  trees,  turpentine  will 
become  a  chemical  curiosity  within  the  lifetime  of  many 
of  us,  unless  new  trees  are  planted. 

217 


2i8  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

American  differs  from  Russian  turpentine  in  odor  and 
in  specific  gravity,  although  in  chemical  composition  they 
are  alike.  The  specific  gravity  of  American  turpentine 
is  about  .865  when  fresh,  but  it  will  rise  as  high  as  .90 
when  old.  It  is  supposed  to  boil  at  350°  F.,  but  that  also 
depends  very  largely  on  the  condition  of  the  turpentine 
and  whether  it  has  been  exposed  to  the  air.  Turpentine 
flashes  according  to  the  text-books,  and  according  to  the 
majority  of  specifications  that  are  written,  at  105°  F. 
As  a  matter  of  fact,  its  flash  point  is  98°  F.  Turpentine 
evaporates  very  slowly,  and  on  account  of  this  slow 
evaporation  it  is  very  highly  prized  as  a  varnish  diluent, 
but  there  are  paraffin  products  that  have  lately  been 
invented  that  evaporate  just  as  slowly  and  leave  no  resi- 
due behind.  Pure  turpentine  when  poured  on  a  sheet 
of  filter  paper  should  leave  absolutely  no  residue  behind, 
and  a  drop  of  water  poured  on  the  paper  after  the  tur- 
pentine has  evaporated  must  be  absorbed  as  readily  by 
the  paper  as  before  it  was  immersed.  In  this  regard  the 
petroleum  naphtha  solvents  are  identical.  They  will  be 
described  in  the  proper  chapter. 

The  following  organic  analyses  of  French,  American, 
and  wood  turpentines  show  that  French  turpentine  and 
American  turpentine  are  both  represented  by  the  for- 
mula CioHie,  the  American  turpentine  being  practically 
100  per  cent  pure.  Wood  turpentine,  however,  may  be 
shown  to  be  97.7  pure,  the  2\  per  cent  of  impurities  con- 
sisting of  pyridene  bases,  formalin,  and  other  wood 
decomposition  products.  Since  these  investigations  were 
made  in  1905,  samples  of  wood  turpentine  have  been 
placed  on  the  market  which  are  so  nearly  identical  with 
the  sap  turpentine  that  it  is  almost  impossible  to  dis- 
tinguish them,  only  an  experienced  consumer  being  able 
to  tell  the  difference,  the  wood  turpentine  having  a  pe- 


TURPENTINE 


219 


culiar  odor  which  is  lacking  in  the  sap  turpentine.     No 
matter   how   thoroughly   a   wood   turpentine   is   purified, 

there  is  always  a  smell  of  sawdust  which  clings  to  it  and 
which  can  be  recognized  by  a  person  once  familiar  with 

the  odor.     These  pure  grades  of  wrood  turpentine  cannot 
be  said  to  be  adulterants  of  the  sap  turpentine. 

FRENCH  TURPENTINE 

First  Analysis  Second  Analysis 

Weight  of  sample o.  2040  grams.  o.  1870  grams. 

CC>2  obtained 0.6558  grams.  0.6009  grams. 

HoO  obtained o.  2161  grams.  o.  1980  grams. 

Hence,  percentage  composition, 

Carbon 87 . 67  per  cent.  87 . 63  per  cent. 

Hydrogen 11.87  Per  cent.  11.87  Per  cent. 

Total 99-54  per  cent.  99 . 50  per  cent. 

AMERICAN  TURPENTINE 

First  Analysis  Second  Analysis 

Weight  of  sample o.  1777  grams.  o.  1828  grams. 

CO2  obtained O-57I4  grams.  0.5878  grams. 

H2O  obtained o.  1923  grams.  o.  1968  grams. 

Hence,  percentage  composition, 

Carbon 87 . 70  per  cent.  87 . 69  per  cent. 

Hydrogen 12.12  per  cent.  12.07  Per  cent- 
Total  99 . 82  per  cent.  99 .  76  per  cent. 

WOOD  TURPENTINE 

First  Analysis  Second  Analysis 

Weight  of  sample o.  1891  grams.  o.  1656  grams. 

CO2  obtained o-  5939  grams.  0.5202  grams. 

H>O  obtained o.  2042  grams.  o.  1785  grams. 

Hence,  percentage  composition, 

Carbon 85 . 65  per  cent.  85 . 67  per  cent. 

Hydrogen 12.10  per  cent.  1 2 . 08  per  cent. 

Oxygen 2.25  per  cent.  2 . 25  per  cent. 

Total 100.00  per  cent.  100.00  per  cent. 


220  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

In  the  Journal  of  the  American  Chemical  Society 1 
for  1904  a  very  exhaustive  treatise  is  given  on  spirits  of 
turpentine,  in  which  it  is  demonstrated  that  the  only 
reliable  chemical  test  for  differentiating  between  wood 
turpentine  and  the  old  spirits  is  the  determination  of  the 
iodine  absorption  number.  But  even  this  is  now  growing 
to  be  very  unreliable,  for  the  reason  that  so  much  care 
and  skill  is  exercised  in  the  manufacture  of  wood  tur- 
pentine that  it  is  almost  impossible  to  distinguish  it 
from  the  sap  turpentine.  A  great  deal  has  been  written  on 
the  optical  activity  of  turpentine  when  observed  through 
the  polariscope.  The  paint  chemist,  however,  cannot 
point  with  any  degree  of  certainty  to  this  test,  excepting 
where  a  coarse  mixture  of  benzine,  rosin  oil,  etc.,  is  made, 
and  up  to  the  present  writing  very  highly  refined  tur- 
pentine and  sap  turpentines  show  little  or  no  difference. 
The  admixture  of  rosin  oil,  benzine,  benzene,  kerosene, 
and  adulterants  of  that  kind  are,  of  course,  differentiated 
with  more  or  less  ease. 

Turpentine  is  by  no  means  used  as  largely  as  it  was 
prior  to  1906.  The  reason  for  this,  strange  to  say,  is  a 
moral  one  and  not  a  physical  one.  Ten  years  ago  it 
would  have  been  thought  impossible  to  do  without  spirits 
of  turpentine  in  paint  or  varnish.  Today  it  is  used  by 
many  people  who  think  they  have  to  use  it,  and  by  others 
who  use  it  in  high  grade  piano  and  other  finishing  varnishes, 
because  they  believe  it  gives  a  physical  flow  to  the  varnish 
which  cannot  be  obtained  by  the  use  of  anything  else. 
This,  however,  is  disputed  by  many  manufacturers.  At 
any  rate,  the  fact  remains  that  several  years  ago  turpentine 
rose  from  a  price  of  about  40  cents  per  gallon  to  $1.13, 
for  a  number  of  men  in  the  southern  part  of  the  United 
States  attempted  to  corner  the  market.  Before,  how- 

1  "Analysis  of  Turpentine,"  by  Jno.  M.  McCandless,  p.  981,  1904. 


TURPENTINE  221 

ever,  the  price  reached  the  abnormal  figure  of  $1.13  some 
of  the  officials  of  the  United  States  Navy  made  exhaust- 
ive experiments  and  showed  that  the  turpentine  sub- 
stitutes of  the  petroleum  type  were  absolutely  as  good 
and  served  the  same  purpose  as  spirits  of  turpentine. 
Not  to  go  into  the  details  of  this,  about  five  years  ago 
the  United  States  Navy  substituted  some  70,000  gallons 
of  turpentine  by  turpentine  substitute,  and  the  resulting 
paint  gave  just  as  good  service  and  the  saving  in  price 
was  very  great.  The  men  who  had  attempted  to  corner 
the  market  and  enrich  themselves  at  the  expense  of  others 
were  finally  ruined,  and  the  whole  turpentine  industry 
received  a  staggering  blow,  from  which  at  this  date  it 
has  not  entirely  recovered.  The  price  dropped  until  it 
hovered  around  40  and  50  cents,  but  in  the  meantime 
the  paint  industry  had  learned  the  lesson,  which  was  of 
tremendous  value,  that  it  could  do  without  turpentine 
entirely. 

TURPENTINE1 

Distillation  of  Pure  Gum  Spirits  of  Turpentine 
Will  not  begin  distilling  lower  than  153°    C. 

i    to  2%  distills  over  by  153°  C. 
50%  "         "      "   i57°  C. 

80%  "      "   159°  C. 

85%  "         "      "   160°  C. 

95%  "         "      "   165-5°  C. 

Sometimes 

50%  «         "      "   159°  C. 

80%  "         "      "   i6o°C. 

85%  "      "   i6i°C. 

95%   should  be  distilled  by  165.5°  C. 

1  Data  from  J.  E.  Teeple,  New  York  City. 


222  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Distillation  of  Steam  Distilled  Wood  Turpentine 
Usually  begins  distilling  at  about  153°  C. 
50%  distills  over  by  160°  C. 
80%        "         "      "   164°  C. 
85%       "         "      "   165.5°  C. 
95%       "        "      "   i75°  C. 
Sometimes 

80%       "         "      "   163°  C. 
85%        "         "      "   164°  C. 
90%       "         "      "   165.5°  C. 
95%       "         "      "   172°  C. 

This  latter  would  be  considered  a  very  good  grade. 
Sometimes  only  60%  to  70%  will   distill  by    165.5°  C.  —  Poor 
grade. 

WOOD  TURPENTINE 

The  turpentine  in  the  United  States  is  held  in  such 
strong  hands  that  the  price  is  abnormally  high,  and  within 
the  last  five  years  pine,  sawdust,  shavings,  tree  stumps, 
and  old  logs  have  been  placed  in  retorts  and  distilled 
in  the  same  manner  as  the  sap  of  the  pine  tree.  A  liquid 
is  obtained  which  is  sold  under  the  name  of  wood  tur- 
pentine and  is  guaranteed  by  many  to  be  absolutely  the 
same  material  as  that  obtained  from  the  sap  of  the 
tree.  It  must  be  frankly  admitted  that  there  are  some 
wood  turpentines  on  the  market  at  this  writing  which 
are  so  similar  to  the  real  article  that  it  is  almost  impos- 
sible to  differentiate  between  them.  And  yet  there  is 
always  a  peculiar  distinctive  odor  to  these  wood  tur- 
pentines which  does  not  exist  in  the  pure  turpentines. 
Several  organic  analyses  of  this  variety  of  wood  tur- 
pentine by  the  author  have  shown  that  the  formula 
is  not  CioHie,  but  that  it  is  a  most  complex  mixture  con- 
taining more  than  a  trace  of  pyridene  bases,  formic  acid, 


TURPENTINE  223 

formaldehyde,  and  other  products  from  the  destructive 
distillation  of  wood.  But  wood  turpentine  is  being 
improved  so  continually  that  these  impurities  are  being 
largely  removed.  For  exterior  painting,  wood  turpen- 
tine that  contains  only  a  trace  of  these  impurities  is 
just  as  good  as  the  sap  turpentine,  and  for  indoor  paint- 
ing it  is  no  better  than  a  number  of  the  petroleum 
products  and  costs  very  much  more  money.  It  cannot 
be  said  that  it  has  advantages  in  exterior  painting  over 
the  benzine  products.  One  reason  why  it  can  be  used  on 
exterior  work  and  not  on  interior  work  is  that  the  dis- 
agreeable odor  it  sometimes  gives  off  becomes  obnoxious 
to  those  who  use  it  on  interior  work.  The  pure  grades 
of  wood  turpentine  cost  within  5  cents  per  gallon  of  the 
price  of  sap  turpentine,  and  judging  from  the  large 
number  of  concerns  that  have  sprung  up  within  the  last 
five  years  for  the  manufacture  of  wood  turpentine  and 
then  slowly  disappeared,  it  is  reasonable  to  infer  that  the 
industry  is  not  profitable. 

AMERICAN   SOCIETY   FOR  TESTING  MATERIALS,   PHILADELPHIA, 

PA.,   U.S.A.,   AFFILIATED   WITH  THE   INTERNATIONAL 

ASSOCIATION  FOR  TESTING  MATERIALS 

STANDARD  SPECIFICATIONS  FOR  TURPENTINE 

Serial  Designation:  D  13-15 

The  specifications  for  this  material  are  issued  under  the  fixed 
designation  D  13;  the  final  number  indicates  the  year  of  original 
issue,  or  in  the  case  of  revision,  the  year  of  last  revision.  Adopted, 
1915. 

General.  —  i.  These  specifications  apply  both  to  the  turpentine 
that  is  distilled  from  pine  oleoresins,  and  commonly  known  as  "  gum 
turpentine"  or  "spirits  turpentine,"  and  to  the  turpentine  commonly 
known  as  "wood  turpentine"  that  is  obtained  from  resinous  wood, 
whether  by  extraction  with  volatile  solvents,  or  by  steam,  or  by  de- 
structive distillation. 


224  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

2.  The  purchaser,  when  ordering  under  these  specifications,  may 
specify  whether  gum  spirits  or  wood  turpentine  is  desired. 

The  turpentine  shall  be  clear  and  free  from  suspended  matter 
and  water. 

Color.  —  3.  The  color  shall  be  "Standard"  1  or  better. 

Specific  Gravity.  —  4.  The  specific  gravity  shall  be  not  less  than 
0.862  nor  more  than  0.872  at  15.5°  C. 

Refractive  Index.  —  5.  The  refractive  index  at  15.5°  C.  shall  be 
not  less  than  1.468  nor  more  than  1.478. 

Initial  Boiling  Point.  —  6.  The  initial  boiling  point  shall  be  not 
less  than  150°  nor  more  than  160°  C. 

Distillation.  —  7.  Ninety  per  cent  of  the  turpentine  shall  distill 
below  170°  C. 

Polymerization.  —  8.  The  polymerization  residue  shall  not  ex- 
ceed 2  per  cent  and  its  refractive  index  at  15.5°  C.  shall  not  be  less 
than  1.500. 

METHODS  OF  ANALYSIS 

9.  Color.  —  Fill  a  2oo-mm.,  perfectly  flat  bottom  colorimetric 
tube  graduated  in  millimeters  to  a  depth  of  from  40  to  50  mm.  with 
the  turpentine  to  be  examined.     Place  the  tube  in  a  colorimeter  and 
place  on  or  under  it  a  No.  2  yellow  Lovibond  glass.     Over  or  under  a 
second  graduated  tube  in  the  colorimeter,  place  a  No.  i  yellow  Lovi- 
bond glass  and  run  in  the  same  turpentine  until  the  color  matches  as 
nearly  as  possible  the  color  in  the  first  tube.     Read  the  difference 
in  depth  of  the  turpentine  in  the  two  tubes.    If  this  difference  is  50 
mm.  or  more,  the  turpentine  is  "Standard"  or  better. 

10.  Specific  Gravity.  —  Determine  specific  gravity  at  any  con- 
venient temperature  with  a  plummet,  the  displacement  of  which  has 
been  accurately  determined  for  that  temperature,  or  by  an  equally 
accurate  method,  using  the  factor  0.00082  for  each  degree  centigrade 
that  the  temperature  of  determination  differs  from  15.5°  C. 

11.  Refractive  Index.  —  Determine  refractive  index  at  any  con- 
venient temperature  with  an  accurate  instrument,  and  calculate  the 
results  to  15.5°  C.,  using  the  factor  0.00045  for  each  degree  that  the 
temperature  of  determination  differs  from  15.5°  C. 

1  The  term  "Standard"  refers  to  the  color  recognized  as  standard 
by  the  "Naval  Stores  Trade."  Turpentine  is  of  "Standard"  color 
when  a  depth  of  50  mm.  in  a  perfectly  flat  polished  bottom  tube 
approximately  matches  a  No.  i  yellow  Lovibond  glass. 


TURPENTINE 


225 


12.  Distillation.  —  Use  an  ordinary  Engler  flask  and  condenser,1 
and  heat  the  flask  by  placing  it  in  a  glycerin  or  oil  bath  of  the  general 
type  described  in  Bulletin  No.  135,  Bureau  of  Chemistry.     Fit  the 
flask  with  a  thermometer  reading  from  145°  to  200°  C.  in  such  a  way 
that  the  mercury  bulb  shall  be  opposite  the  side  tube  of  the  flask 
and  the  175°  mark  below  the  cork.     Place  100  cc.  of  the  turpentine 
to  be  examined  in  the  flask,  connect  with  the  condenser,  insert  stopper 
bearing  thermometer,  and  heat  until  distillation  of  the  turpentine 
begins.     Conduct  the  distillation  so  that  the  distillate  passes  over 
at  the  rate  of  2  drops  per  second.     Note  the  initial  distilling  tempera- 
ture and  the  percentage  distilling  below  170°  C. 

13.  Polymerization.  —  Place  20  cc.  of  exactly  38  N  (100.92  per 
cent)  sulphuric  acid  in  a  graduated,  narrow-neck  Babcock  flask,  stop- 
pered, and  place  in  ice  water  and  cool.     Add  slowly  5  cc.  of  the  tur- 
pentine to  be  tested.     Gradually  mix  the  contents,  cooling  from  time 
to  time,  and  not  allowing  the  temperature  to  rise  above  about  60°  C. 
When  the  mixture  no  longer  warms  up  on  shaking,  agitate  thoroughly 
and  place  the  bottle  in  a  water  bath  and  heat  from  60°  to  65°  C.  for 
about  10  minutes,  keeping  the  contents  of  the  flask  thoroughly  mixed 
by  vigorous  shaking  five  or  six  times  during  the  period.     Do  not 
stopper  the  flask  after  the  turpentine  has  been  added,  as  it  may 
explode.     Cool  to  room  temperature,  fill  the  flask  with  concentrated 
sulphuric  acid  until  the  unpolymerized  oil  rises  into  the  graduated 
neck.     Centrifuge  at  about  1200  r.  p.  m.  from  4  to  5  minutes,  or  allow 
to  stand  for  12  hours.     Read  unpolymerized  residue,  notice  its  con- 
sistency and  color,  and  determine  its  refractive  index. 

NAVY  DEPARTMENT  SPECIFICATIONS 
TURPENTINE 

General  Characteristics.  —  i.  The  turpentine  must  be  either  a 
properly  prepared  distillate  of  oleo-resinous  exudation  of  the  proper 
kinds  of  pine,  unmixed  with  any  other  substance,  with  the  character- 
istic sweet  odor  of  gum  turpentine,  or  it  must  be  pure  wood  spirits 
of  turpentine,  refined,  and  freed  from  heavy  oils  and  empyreumatic 
or  pyroligneous  odors  by  steam  distillation;  both  of  the  above  shall 
be  clear  and  water-white. 

Specific  Gravity.  —  2.  The  specific  gravity  shall  not  be  below 
0.862  or  above  0.872  at  15.5°  C. 

1  Stillman,  "Engineering  Chemistry,"  p.  503. 


226  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Refractive  Index.  —  3.  The  refractive  index  shall  not  be  less  than 
1.468  nor  greater  than  1.476  at  20°  C. 

Boiling  Point. — 4.  The  boiling  point  shall  be  between  152°  C. 
and  158°  C. 

Distillation  Test.  —  5.  When  200  c.c.  of  the  turpentine  is  dis- 
tilled, 95  per  cent  should  pass  over  below  170°  C. 

For  this  test  use  a  300  c.c.  flask,  8  cm.  in  diameter,  with  a  side 
tube  8  cm.  from  the  main  bulb,  and  the  neck  extending  8  cm.  above 
the  side  tube.  The  neck  is  2  cm.  in  diameter  and  the  side  tube  is 
5  m.  m.  This  flask  should  be  fitted  with  a  thermometer  (reading 
from  145°  to  200°  C.)  immersed  in  the  vapor.  The  mercury  bulb 
should  be  opposite  the  side  tube  of  the  flask  and  the  reading  175°  C. 
should  be  below  the  cork.  The  distillation  should  be  so  conducted 
that  there  shall  pass  over  about  two  drops  of  the  distillate  per  second. 

Polymerization.  —  6.  When  5  c.c.  of  the  sample  is  treated  with 
sulphuric  acid  of  specific  gravity  1.84,  according  to  the  method  herein 
outlined,  there  shall  remain  undissolved  at  the  end  of  thirty  minutes 
not  over  0.09  c.c.  The  residue  unpolymerized  should  show  a  refrac- 
tion value  between  1.50  to  1.52.  It  should  be  viscous  in  nature.  If 
the  residue  is  water-white,  limpid,  and  does  not  show  proper  refrac- 
tion value,  it  should  be  carefully  polymerized  with  38  N  sulphuric 
acid  according  to  Veitch  (see  p.  30,  Bull.  135,  or  Cir.  85,  Bureau  of 
Chemistry,  U.  S.  Department  of  Agriculture). 

Method  of  Polymerization.  —  7.  Add  slowly  5  c.c.  of  the  turpen- 
tine to  25  c.c.  sulphuric  acid,  1.84,  contained  in  an  ordinary  graduated 
narrow-necked  Babcock  flask.  Shake  the  flask  with  a  rotary  motion 
to  insure  gradual  mixing.  Cool,  if  necessary,  in  ice  water,  not  per- 
mitting the  temperature  to  rise  above  60°  to  65°  C.  Agitate  thor- 
oughly and  maintain  at  about  65°,  with  frequent  agitations,  for  one 
hour.  Cool.  Fill  the  flask  with  H^SCu,  bringing  the  unpolymerized 
oil  into  the  graduated  neck.  Allow  to  stand  one  hour.  Read  off 
unpolymerized  content,  note  its  consistency  and  color,  and  determine 
its  refractive  index. 

Color  Test.  —  8.  Shake  10  c.c.  of  the  turpentine  with  10  c.c.  of 
concentrated  hydrochloric  acid  in  a  test  tube.  The  development, 
after  three  minutes'  standing,  of  a  decided  red  color  is  indicative  of 
the  presence  of  other  usually  heavy  resinous  oils. 

Evaporation  Test.  —  9.  When  10  c.c.  of  the  sample  are  placed  in 
a  glass  crystallizing  dish,  2\  inches  in  diameter  and  if  inches  high, 
and  evaporated  on  an  open  steam  bath,  with  a  full  head  of  steam,  for 


TURPENTINE  227 

three  hours,  the  amount  of  residue  shall  not  weigh  more  than  0.15 
gram.  A  single  drop  allowed  to  fall  on  clean  white  paper  must  com- 
pletely evaporate  at  a  temperature  of  20°  C.  without  leaving  a  stain. 

Flash  Point.  —  10.  The  turpentine  must  not  flash  below  34°  C.  in 
Abel's  enclosed  tester. 

ii.  Bidders  must  state  specifically  on  proposals  whether  they 
propose  to  furnish  steam  distilled  wood  turpentine  or  pure  gum 
spirits  of  turpentine. 


CHAPTER  XVIII 


ONE  of  the  industries  which  has  developed  as  a  result 
of  the  policy  of  conservation  in  the  United  States  is  the 
manufacture  of  useful  products  from  resinous  woods. 
Enormous  quantities  of  the  latter,  which  in  previous 
years  were  considered  of  little  or  no  use  and  were  deliber- 
ately burned  in  huge  burners  especially  constructed  for 
the  purpose,  or  which  were  simply  allowed  to  go  to  waste, 
are  now  being  economically  and  profitably  manipulated 
for  the  recovery  of  turpentine,  pine  oil,  and  rosin,  or  the 
production  of  tar  oils,  pine  pitch,  and  charcoal. 

The  two  commercially  important  methods  in  vogue 
are,  first,  the  steam  and  solvent  or  extraction  process,  and 
second,  the  destructive  distillation  process. 

H.  T.  Yaryan2  has  taken  out  letters  patent  on  a 
process  for  extracting  turpentine  and  rosin  from  resinous 
woods,  which  very  well  illustrates  the  extraction  method 
as  practised  today.  Resinous  wood,  reduced  to  fine 
chips  by  passing  through  a  wood  chipper,  is  charged  into 
an  iron  vessel  through  a  charging  door  at  the  top.  The 
wood  rests  upon  a  false  bottom  over  a  coil  supplied  with 
superheated  steam  for  producing  and  maintaining  the 

1  Journal  of  Society  of   Chemical  Industry,  June  15,  1914,    No.   n,  Vol. 
xxxiii,  by  Maximilian  Toch. 

2  The  following  is  a  list  of  the  Yaryan  U.  S.  Patents: 

No.  915,400,  March  16,  1909  934,257,  September  14,  1909 

915.401,  March  16,  1909  964,728,  July  19,  1910 

915.402,  March  16,  1909  992,325,  May  16,  1911 
922,369,  May  18,  1909 

228 


PINE  OIL  229 

proper  temperature  within  the  iron  chamber.  The  door 
at  the  top  and  the  discharge  door  at  the  bottom  are 
closed,  and  the  current  of  superheated  steam  is  driven 
into  the  mass  of  chips.  This  is  continued  until  the  more 
volatile  turpentine  has  been  vaporized  and  driven  over 
into  the  condensers.  The  wood  in  the  extraction  vessel 
is  left  charged  with  a  small  percentage  of  heavy  turpen- 
tine, together  with  pine  oil  and  rosin.  Steam  is  shut  off, 
the  excess  moisture  in  the  hot  wood  is  removed  by 
connecting  the  vessel  with  a  vacuum  pump,  and  finally 
a  liquid  hydrocarbon  (boiling  point,  24O°-2rjo°  F.)  is 
sprayed  over  the  top  and  allowed  to  percolate  down 
through  the  pores  of  the  wood.  The  resinous  materials 
are  thus  thoroughly  and  completely  extracted,  and  passed 
into  a  storage  tank,  from  which  they  are  pumped  into  a 
still  used  for  separating  the  component  parts  of  the  solu- 
tion. From  the  still  the  hydrocarbon  solvent  is  readily 
separated  from  the  heavier  pine  oils  by  distillation  under 
reduced  pressure,  on  account  of  the  great  difference  in 
the  boiling  point  between  the  pine  oils  and  the  hydro- 
carbon solvent,  the  former  boiling  between  350°  and  370°  F. 
The  pine  oils  are  in  turn  separated  from  the  rosin  by 
distillation  with  superheated  steam. 

Other  so-called  "low  temperature"  processes  deserve 
mention  as  possessing  features  of  merit,  although  sufficient 
data  does  not  appear  to  be  available  to  show  their  true 
value  when  operated  on  a  large  commercial  scale.  The 
Hough  process,  for  example,  is  to  be  considered  essentially 
a  preliminary  treatment  in  the  manufacture  of  paper 
pulp  from  resinous  woods.  Chipped  wood  is  placed  in  a 
retort  and  subjected  to  the  action  of  a  dilute  alkali.  The 
rosins  are  saponified  and  the  soap  separated  from  the 
alkaline  liquor  by  cooling  and  increasing  the  alkali  con- 
centration to  the  desired  degree.  The  rosin  soap  may  be 


230  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

sold  as  such,  or  treated  with  acids  for  recovery  of  the 
rosin.  The  turpentine  and  pine  oils  are  recovered  either 
by  preliminary  treatment  with  steam  or  during  the  early 
stages  of  the  cooking  process. 

It  will  be  noted  that  in  the  low  temperature  processes 
the  only  products  recovered  are  turpentine,  pine  oils, 
and  rosins,  the  first  two  removed  by  the  action  of  steam, 
either  saturated  or  superheated,  and  the  latter  by  extrac- 
tion by  use  of  a  neutral  volatile  solvent  or  a  saponifying 
agent.  The  so-called  "spent  wood"  may  be  used  either 
for  the  manufacture  of  paper  pulp  or  as  a  fuel  to  generate 
the  power  necessary  to  carry  out  the  process. 

In  the  destructive  distillation  process,  the  wood,  in  the 
form  of  cordwood  4  ft.  to  6  ft.  in  length  and  4  in.  to  8  in. 
in  diameter,  is  placed  in  a  horizontal  retort  and  the  tem- 
perature gradually  raised  until  the  wood  is  thoroughly 
carbonized.  The  factor  of  greatest  importance  in  the 
successful  operation  of  this  process  is  temperature  control, 
as  it  is  essential  that  the  turpentines  and  pine  oils  be 
removed  in  so  far  as  is  possible  before  the  temperature  at 
which  the  rosins  and  wood  fibre  begin  to  decompose  is 
reached.  The  total  volume  of  distillate,  as  well  as  the 
percentage  volume  of  each  of  the  several  fractions  thereof, 
is  largely  dependent  on  the  degree  of  temperature  control. 

Destructive  distillation  of  resinous  wood  was  first 
carried  out  in  earthen  trenches,  the  combustion  being 
controlled  by  partially  covering  the  wood  with  earth. 
Tar  and  charcoal  were  the  only  products  recovered. 
Then  came  the  beehive  oven,  operated  in  much  the  same 
crude  manner,  but  recovering  the  more  volatile  distillates, 
in  addition  to  tar  and  charcoal.  This  was  in  turn  super- 
seded by  the  horizontal  retort,  externally  heated,  hot 
gases  being  circulated  either  through  an  outer  shell  or 
through  pipes  within  the  retort.  Next  came  the  bath 


PINE  OIL  231 

process,  wherein  the  cordwood  was  immersed  in  a  bath  of 
hot  pitch  or  rosin,  thereby  volatilizing  the  turpentine  and 
lighter  pine  oils  and  dissolving  the  heavier  oils  and  rosins. 
After  this  preliminary  treatment  the  bath  was  withdrawn 
and  the  wood  subjected  to  straight  destructive  distillation. 

More  recently 1  a  retort  has  been  devised  utilizing  the 
basic  principle  of  the  laboratory  oil  bath.  The  retort  is 
heated  by  means  of  a  layer  of  hot  petroleum  oil  which  is 
kept  continually  circulating  between  the  retorts  and  an 
outer  cylindrical  shell  that  completely  surrounds  the  re- 
tort proper.  In  this  way  it  is  claimed  that  the  tempera- 
ture of  distillation  can  be  accurately  controlled.  The 
turpentine  and  pine  oil  obtained  are  fractionated  and 
rectified  by  subsequent  steam  distillation.  In  running  the 
retort  the  temperature  of  the  oil  bath  is  so  regulated  that 
the  heat  inside  does  not  exceed  450°  F.  before  all  the 
turpentine  and  pine  oil  have  been  distilled. 

The  products  of  destructive  distillation  by  the  several 
processes  are  in  each  case  of  very  much  the  same  general 
nature,  namely,  turpentine,  pine  oils,  tar  oils,  pine  tar, 
pitch,  and  charcoal.  In  some  instances  low-grade  rosin 
oils  are  also  produced. 

"Light  wood"  does  not  refer  to  woody  fibre  which 
has  a  low  specific  gravity.  The  name  originated  from 
the  fact  that  this  particular  wood  is  so  rich  in  oil  and 
resinous  material  that  it  is  readily  used  for  lighting  fires. 
In  the  southern  portion  of  the  United  States  little  bundles 
of  "light  wood"  are  for  sale  in  strips  about  |  inch  in 
diameter  and  i  foot  long.  When  a  flame  is  applied  to 
one  of  these  strips  of  wood  it  becomes  useful  for  lighting 
fires,  hence  the  name  "light  wood."  The  author  has  seen 
"light  wood"  so  rich  in  resins  and  oily  material  that  by 
transmitted  light  a  thin  section  looked  like  translucent 

1  T.  W.  Pritchard,  Journal  of  Society  of  Chemical  Industry,  1912,  31,  418. 


232  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

ruby  glass.  It  is  this  particular  wood  which  is  most 
used  for  the  distillation  of  wood  turpentine,  pine  oil,  and 
rosin. 

The  product  from  that  type  of  pine  tree  from  which 
turpentine  is  obtained  has  always  been  regarded  as  pro- 
ducing two  materials  when  the  sap  has  been  collected  and 
distilled.  The  one  material  is  turpentine,  and  the  other 
rosin.  About  ten  years  ago,  when  destructive  and  steam 
distillation  of  pine  wood  became  a  practical  industry,  a  third 
substance  was  recovered.  This  material,  intermediate  be- 
tween turpentine  and  rosin,  is  now  known  as  "pine  oil." 

As  far  as  the  author  knows,  no  one  has  yet  determined 
the  chemical  constitution  of  this  intermediate  product  of 
the  pine  tree,  which  has  been  designated  as  "pine  oil." 
Two  years  ago  the  writer  started  this  investigation,  which 
is  practically  finished.  There  is  as  yet  no  standard  of 
purity  for  pine  oil,  but  that  it  has  a  definite  chemical 
composition  is  now  fairly  well  established.  The  only 
original  investigation  of  the  chemical  composition  of  pine 
oil  was  carried  out  by  Dr.  J.  E.  Teeple1  on  long  leaf 
pine  oil. 

Dr.  Teeple  says:  "The  commercial  long  leaf  oil,  as 
it  comes  on  the  market,  is  either  clear  and  water  white, 
containing  3  or  4  per  cent  of  dissolved  water,  or  it  may 
have  a  very  faint  yellow  color  and  be  free  from  dissolved 
water.  The  specific  gravity  ranges  from  0.935  to  °-947> 
depending  on  freedom  from  lower  boiling  terpenes.  A 
good  commercial  product  will  begin  distilling  at  about 
206°  to  210°,  and  75  per  cent  of  it  will  distill  between  the 
limits  2ii°-2i8°  and  50  per  cent  of  it  between  2i3°-2i7°. 
A  sample  having  a  density  of  0.945  at  15.5°  showed  a 
specific  rotation  of  about  [V]  ~  -  -  11°,  and  an  index  of 

1  Journal  of  American  Chemical  Society,  1908,  80,412;  Journal  of  Society 
of  Chemical  Industry,  1908,  346. 


PINE  OIL  233 

refraction  of  ND  1.4830.  In  fractional  distillation  of  the 
oil  the  specific  gravity  of  the  various  distillates  rises 
regularly  with  increasing  temperature,  becoming  steady 
at  about  0.947  at  217°. 

"If  the  oil  consists  essentially  of  terpineol,  Ci0Hi8O, 
it  should  be  easy  to  convert  it  into  terpin  hydrate, 
Ci0H2002  +  H20,  by  the  method  of  Tiemann  and  Schmidt.1 
The  conversion  was  found  to  proceed  easily  when  the  oil 
was  treated  with  5  per  cent  sulphuric  acid,  either  with 
or  without  admixture  with  benzine.  If  agitated  contin- 
uously, the  reaction  is  complete  within  3  or  4  days.  If, 
on  the  other  hand,  the  mixture  is  allowed  to  stand 
quietly,  the  formation  of  terpin  hydrate  extends  over 
several  months  and  produces  most  beautiful  large  crystals, 
which,  without  recrystallizing,  melt  at  ii7°-ii8°.  When 
recrystallized  from  ethyl  acetate  they  melt  at  118°.  The 
yield  is  about  60  per  cent  of  the  theoretical.  This 
forms  such  a  simple,  cheap,  and  convenient  method  of 
making  terpin  hydrate  that  it  will  doubtless  supersede 
the  usual  manufacture  from  turpentine,  alcohol,  and 
nitric  acid,  and  instead  of  terpin  hydrate  serving  as  raw 
material  for  the  manufacture  of  terpineol,  as  heretofore, 
the  reverse  will  be  the  case." 

The  term  "pine  oil,"  as  now  understood,  is  the  heavy 
oil  obtained  from  the  fractionation  of  crude  steam  dis- 
tilled wood  turpentine.  When  the  sap  of  the  pine  tree 
is  subjected  to  distillation  in  a  current  of  steam  the 
volatile  liquid  —  turpentine  —  consists  almost  entirely  of 
the  hydrocarbon,  pinene  (CioHie).  When,  however,  the 
trunk,  stumps,  and  roots  of  the  same  tree  have  been 
allowed  to  remain  on  the  ground  for  a  number  of  years 
and  are  then  steam  distilled,  there  are  obtained,  in  addition 
to  the  turpentine  and  rosin,  certain  heavier  oils  formed 

1  Ber.,  28,  1781. 


234  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

by  hydrolysis  and  oxidation  as  a  result  of  exposure  to  the 
atmosphere.  To  the  heavier  oils  thus  formed  and  yielded 
up  in  the  process  of  steam  distillation  the  term  "pine  oil" 
is  properly  applied. 

Pure  pine  oil  has  a  very  pleasant  aromatic  odor,  similar 
at  times  to  the  oil  of  caraway  seed  or  the  oil  of  juniper 
seed.  When  pine  oil  is  impure  it  is  very  difficult  to  use  it 
for  interior  work  on  account  of  its  pernicious  odor  of 
empyreumatic  compounds.  It  has  been  used  to  a  con- 
siderable extent  for  making  paints  which  should  dry 
without  a  gloss,  and  as  a  "flatting"  material  it  has  been 
very  successful.  It  has  the  excellent  quality  of  flowing 
out  well  under  the  brush  and  of  not  showing  brush  marks, 
the  latter  because  it  evaporates  so  very  slowly.  It  is 
a  very  powerful  solvent,  and  many  of  the  acid  resins 
which  have  a  tendency  to  separate  when  they  are  in- 
sufficiently heated  with  drying  oils  will  remain  together 
when  pine  oil  is  added.  Pine  oil  can  be  used  to  a  con- 
siderable extent  as  a  diluent  in  nitrocellulose  solutions, 
and  as  a  cooling  agent  for  the  reduction  of  varnishes 
it  also  has  excellent  qualities.  The  author  takes  this 
opportunity  of  stating  that  on  previous  occasions  his 
recommendations  concerning  new  and  useful  materials  for 
the  paint  and  varnish  industry  have  been  misunderstood 
in  some  instances,  and  it  is  to  be  hoped  that  these  re- 
marks will  not  be  misinterpreted.  Pine  oil  is  a  new  and 
useful  material,  but  it  is  by  no  means  a  substitute  for 
linseed  oil  or  turpentine  or  any  of  the  other  materials  now 
on  the  market.  It  has  properties  peculiar  to  itself,  and 
when  intelligently  used  is  of  considerable  value. 

Practically  all  the  pine  oil  obtainable  contains  a  small 
percentage  of  water  in  solution,  to  which  it  clings  rather 
tenaciously,  and  it  is  by  no  means  a  simple  matter  to 
dehydrate  this  material.  A  rather  complex  apparatus  for 


PINE  OIL 


235 


E20 


dehydrating  the  material  is  necessary  with  temperature 
control,  but  the  test  which  the  author  has  devised  for 
the  determination  of  water  is  quite  simple.  If  5  c.c.  of 
pine  oil  are  mixed  '°° 
with  i  c.c.  of  a  neu- 
tral mineral  oil,  like 
benzine,  kerosene,  or 
benzol,  and  a  per- 
fectly clear  solution 
is  obtained  on  shak- 
ing, no  water  is  pres- 
ent; but  if  there  is 
any  water  present  in 
the  pine  oil  the  water 
appears  as  a  colloid, 
and  a  milky  solution 
is  obtained  which 
does  not  separate 
after  long  standing.  The  fact  that  pine  oil  will  take  up 
a  considerable  quantity  of  water  and  still  remain  clear 
makes  it  useful  for  emulsion  paints  such  as  are  very  much 
in  vogue  at  the  present  time  for  the  interior  of  build- 
ings, and  it  has  been  suggested  that  the  addition  of  water 
up  to  5  per  cent  for  such  a  purpose  is  beneficial  on 
new  walls.  The  United  States  Bureau  of  Chemistry1  has 
developed  a  method  for  the  determination  of  moisture 
by  the  use  of  calcium  carbide;  this  is  being  investigated 
by  the  author  but  on  account  of  its  being  a  gas-volu- 
metric method  it  is  not  quite  feasible  for  general  use  in 
technical  laboratories. 

A  number  of  commercial  samples  of  pine  .oil  were  de- 
hydrated and  analyzed.  The  tables  following  indicate 
the  results  obtained :  — 

1  U.  S.  Dept.  Agriculture,  Bureau  of  Chemistry,  Circular  97. 


FIG.  VI. 


236 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


»5  > 


.s 


J3          4)          O        .- 

^     -2     "3     -S 
u       g       o       £ 


5_-a 
"  I- 

Is! 


PINE  OIL 


237 


TABLE  II.  —  FRACTIONAL  DISTILLATION  OF  COMMERCIAL  PINE  OIL 


Temperature 


Fraction 

in  % 


Total 
distillate 


Sp.  gr. 
15-5°  C. 


Water,  100°. 
174  —  194.  . 
194  —  205.  . 
205  —  208.  . 

208  210.  -. 

210  213.  . 

213  —  216.  . 

2l6  2l8.  . 

218  — 


2 

5 
II 

IO 
'25 

35 
6 

i 
4 


7 

18 
28 

S3 

88 

94 
95 
99 


0.882 
0.920 
o-933 
Q-939 
0.941 
0.942 
0.942 


TABLE  III.  —  ULTIMATE  ANALYSIS  OF  PINE  OIL 


Sample  Number. 


C. 


H. 


O. 


78.1 

2 77-9 

3 77-o 

4 81.8 

5 8o-9 

6 79-o 

78.4 
79.6 

9 78.3 

Average 79.0 

Terpineol  (theoretical) 77-85 

PVench  turpentine 87.7 

American  turpentine 87.7 

Wood  turpentine 85.7 

Pine  oil,  first  runnings 84.3 

Distillate  pine  oil,  174  —  195°  C 82.6 


11.4 

11. i 
10.6 

10.6 
11.4 

11. 2 

u-5 

11. I 

11. 2 


10.4 
10.7 
II-9 

7.6 

8-5 

9.6 
10.4 

8.9 
10.6 

9-8 


11.77 
11.9 

12. 1 
12. 1 
II.8 
II.4 


10.38 


3-9 
6.0 


CHAPTER  XIX 

BENZINE 

THE  petroleum  products  are  used  very  largely  in  the 
manufacture  of  all  kinds  of  mixed  paints,  the  principal 
one  used  being  that  known  as  "benzine."  It  belongs  to 
the  series  of  organic  compounds  having  the  general  for- 
mula CnEUn  +  2.  Although  it  is  frequently  added  to  paint 
in  its  pure  form  as  a  diluent  it  is  just  as  frequently  added 
in  the  form  of  a  liquid  drier  which  is  a  solution  of  the 
original  thickened  drier  in  benzine. 

Within  the  past  ten  years  benzine  has  been  so  made 
that  its  odor  is  not  very  apparent,  and  there  is  much 
discussion  as  to  whether  benzine  is  a  detriment  to  paint 
or  not.  It  is  hardly  necessary  to  touch  upon  the  moral 
side  of  this  question.  If  a  man  should  order  a  paint 
made  according  to  a  given  specification  and  free  from 
benzine,  or  to  contain  only  turpentine  as  a  diluent,  the 
addition  of  benzine  would  be  a  palpable  fraud.  It  is, 
however,  unnecessary  to  discuss  this  point.  The  prin- 
cipal questions  for  discussion  are,  first,  "Is  a  moderate 
amount  of  benzine  harmful  to  paint?"  Second,  "How 
much  benzine  is  permissible  in  paint?" 

Answering  the  second  question  first,  as  to  how  much 
benzine  is  permissible  in  paint,  that  depends  entirely 
upon  the  paint.  A  thick,  viscous,  ropy  paint  which  is 
so  difficult  to  apply  that  it  will  not  flow  evenly  is  un- 
doubtedly improved  by  the  addition  of  benzine.  It  would 
be  just  as  much  improved  by  the  addition  of  turpentine; 
perhaps  it  would  be  improved  most  by  the  addition  of 

238 


BENZINE  239 

kerosene,  especially  in  the  case  of  very  quick  drying 
paints,  since  kerosene  evaporates  more  slowly  than  either 
benzine  or  turpentine.  In  the  case  of  such  dilution  theory 
fails  and  only  practice  can  dictate  how  much  diluent 
can  be  added.  In  the  case  of  a  dipping  paint  where  the 
even  spreading  of  a  linseed  oil  paint  is  desirable,  and 
the  sudden  evaporation  of  the  solvent  helps  to  produce 
a  uniform  coat,  benzine  cannot  be  replaced  by  any  other 
solvent. 

The  argument  that  is  held  forth  by  many,  that  ben- 
zine is  of  no  value  in  a  structural  iron  paint  for  the 
reason  that  its  rapidity  of  evaporation  lowers  the  dew 
point,  as  then  moisture  is  deposited  as  it  evaporates,  is  a 
most  fallacious  argument,  although  in  theory  it  is  cor- 
rect. Turpentine  will  do  exactly  the  same  thing  and  so 
will  any  other  solvent,  depending  entirely  upon  the 
hygroscopic  condition  of  the  atmosphere.  If  painting  be 
done  in  an  atmosphere  where  the  humidity  is  high  and 
the  temperature  near  the  dew  point,  it  is  always  found  that 
it  makes  very  little  difference  what  solvents  are  used, 
the  condensation  being  apparent  in  any  case.  The 
metallic  structure  itself  lowers  the  dew  point  so  that 
the  painting  is  being  conducted  on  a  film  of  invisible 
water,  to  the  detriment  of  the  paint  and  to  the  detriment 
of  the  metal.  On  the  other  hand  a  series  of  experi- 
ments made  on  this  subject  showed  that  where  the  dew 
point  and  the  humidity  are  high,  condensation  easily 
occurs  even  though  the  percentage  of  moisture  in  the 
atmosphere  is  relatively  small.  (See  "Causes  of  Rust  in 
the  Subway,"  Journal  of  the  Society  of  Chemical  Indus- 
try, 1905,  No.  10,  Vol.  24.)  A  great  advantage  is  to  be 
obtained  by  the  moderate  use  of  benzine,  for  in  brushing 
on  a  quick-drying  paint  containing  benzine  the  evapora- 
tion carries  with  it  much  of  the  moisture  in  the  paint. 


240-  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

The  low  price  of  benzine  in  America  offers  a  great 
temptation  for  its  unlimited  use.  In  France  and  Ger- 
many, where  the  petroleum  products  are  more  expensive 
than  they  are  in  America,  and  more  particularly  in 
France,  benzine  is  not  regarded  so  much  as  an  adulterant. 
However,  the  physical  effects  of  benzine  have  been  so 
thoroughly  overcome  since  turpentine  has  reached  such 
an  abnormal  price,  that  a  number  of  most  excellent 
brands  have  been  placed  on  the  market  as  substitutes, 
all  of  which  are  equal  in  physical  characteristics  to 
pure  spirits  of  turpentine.  The  objection,  of  course, 
to  kerosene  as  a  diluent  in  paint  is  that  it  may  carry 
a  small  percentage  of  paraffin  oil  that  has  a  tendency  to 
produce  a  "bloom"  on  paint  and  particularly  on  varnish. 

Quite  a  large  number  of  petroleum  products  have 
been  placed  on  the  market  which  are  so  closely  analogous 
to  turpentine  that  were  it  not  for  the  odor,  or  lack  of 
odor,  it  would  be  very  difficult  to  differentiate  them.  As 
an  instance  it  may  be  cited  that  turpentine  is  a  better 
solvent  for  some  of  the  mixing  varnishes  and  fossil  and 
semi-fossil  resin  driers  than  benzine,  but  the  newer 
petroleum  or  paraffin  compounds,  some  of  which  have  had 
marked  success,  are  absolutely  identical  in  solvent  power, 
speed  of  evaporation,  and  viscosity,  to  turpentine,  and 
while  the  polymerization  acid  test  would  clearly  show  that 
they  are  not  turpentine,  they  can  by  no  means  be  said  to  be 
inferior  in  working  quality  or  solvent  power  to  turpentine. 
The  method  by  which  these  benzines  are  made  consists 
in  passing  certain  paraffin  oils  over  red-hot  coke  in  con- 
junction with  wood  turpentine.  The  product  which  is 
obtained  has  little  or  no  odor.  Thick  or  viscous  paints, 
particularly  the  varnish  and  enamel  paints,  are  so  much 
improved  by  the  addition  of  these  materials  that  even  an 
inexperienced  painter  will  notice  the  free-flowing  quali- 


BENZINE  241 

ties  of   the  material  to  which  these  diluents  have  been 
added. 

The  petroleum  products  used  in  the  manufacture  of 
paint  are  principally  62°  benzine,  which  means  benzine 
having  a  specific  gravity  of  62°  Baume.  Some  of  the 
other  naphthas  ranging  from  71°  to  88°  are  used,  but 
these  are  so  light  and  bring  so  much  higher  prices  than 
the  62°  that  they  are  not  used  as  much  as  the  62°  naph- 
tha. The  newer  grades,  however,  which  approach  tur- 
pentine in  physical  characteristics,  must  be  counted  on  as 
an  important  factor  in  paint  on  account  of  the  extremely 
high  price  of  turpentine,  and  the  fact  that  it  is  strongly 
held  in  a  few  hands.  On  account  of  the  decreasing  amount 
of  this  product,  substitutes  must  be  recognized.  After 
all,  any  solvent,  whether  it  be  benzine,  turpentine, 
naphtha,  benzol  or  acetone,  is  nothing  but  a  solvent  and 
evaporates  completely,  leaving  the  other  vehicles  to  pro- 
tect the  paint.  Of  course,  too  much  solvent  is  a  detri- 
ment to  paint,  no  matter  what  kind  it  may  be. 

BENZINE  1 

Engler  Distillation  of  Commercial  88°  Naphtha 

Sp.  Gr.  (Westphal) 1 5 . 6°  C o .  65 1 

Np  25° 1-3695 

Temperature 
50° 

50°  to  75° 
75°  to  100° 
Residue 

Engler  Distillation  of  Commercial  62°  Naphtha 

Sp.  Gr.  (Westphal) 15.6° o.  732 

Np  25° i .  4106 

1  Richardson  &  Mackenzie,  Amer.  J.  of  Sc.  XXIX,  May,  1910. 


%wt. 

Sp.  Gr.  is.6°C. 

NP25° 

47-7 

0.609 

i  -36°5 

29..  2 

0.65 

I-3756 

6.8 

0.70 

1-393° 

i-4 

1.4061 

242  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


Temperature 

%Wt. 

Sp.  Gr.  20°  /2o°  C. 

NP25° 

o 

5° 

50°  to    7s° 

I  .  2 

8  o 

v)                                         /   O 

75°  to  100° 

2O.  O 

0.7029 

I-3956 

100°  to  125° 

51-9 

0.7286 

i  .4061 

125°  to  150° 

24.6 

0.7462 

1.4168 

Residue 

0.2 

i  .4.282 

CHAPTER  XX 

TURPENTINE  SUBSTITUTES  l 

WHEN  coal  is  distilled  in  the  dry  form  volatile  hydro- 
carbon gases  are  liberated,  which  when  condensed  form  a 
liquid  which  has  great  value  in  the  arts,  and  is  generally 
called  crude  benzol.  Its  composition  really  is  about  60 
per  cent  of  benzol,  the  balance  being  toluol,  xylol  and 
solvent  naphtha.  The  latter  three  are  homologues  of 
benzol.  It  is  estimated  that  over  forty  million  gallons 
of  these  solvents  have  been  wasted  in  the  United  States 
in  smoke  and  vapor  in  the  manufacture  of  coke,  but  at 
this  writing  great  efforts  are  being  made  to  collect  the 
vapors  economically  and  to  put  in  additional  ovens  for 
the  manufacture  of  these  by-products,  so  that  it  is  very 
likely  that  both  benzol  and  toluol  will  soon  be  sold  again 
at  normal  prices.  At  this  writing  both  benzol  and  toluol 
have  risen  from  25  and  30  cents  per  gallon  to  $1.25  and 
$7.00  per  gallon  respectively,  owing  to  the  great  European 
war  and  to  the  small  amount  of  benzol  and  toluol  manu- 
factured in  the  United  States.  These  materials  have 
been  sought  for  very  eagerly  for  the  manufacture  of  both 
carbolic  and  picric  acids  and  trinitrotoluol. 

BENZOL 

This  material  was  for  many  years  known  under  the 
name  of  benzene,  and  here  it  must  be  noted  that  the 
benzene  which  is  equivalent  to  benzol  is  always  spelled 

1  In  the  chapter  on  "Turpentine"  the  author  has  related  how 
turpentine  substitutes  came  into  their  own  on  account  of  the  excessive 
price  of  turpentine. 

243 


244  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

benzene,  and  the  light  naphtha  obtained  from  paraffin 
crude  oil  is  spelled  benzine. 

Benzol  is  the  first  volatile  liquid  which  is  recovered 
when  coal  tar  is  distilled.  Benzol  when  pure  is  color- 
less, has  a  pleasant  odor,  a  specific  gravity  of  0.879  and 
a  boiling  point  of  191°  F.  It  flashes  practically  at  air 
temperature.  It  crystallizes  into  a  solid  at  the  freezing 
point  of  water  and  has  a  peculiar  analogy  to  water 
inasmuch  as  it  melts  again  at  about  37°  F.  It  is  insoluble 
in  water  but  is  soluble  in  alcohol,  ether  and  petroleum 
naphtha.  Its  formula  is  C6H6;  it  attacks,  though  it 
does  not  dissolve,  all  forms  of  linoxyn,  which  it  wrinkles 
and  removes  from  the  base.  It  is  for  this  reason  that 
it  is  so  valuable  as  a  paint  remover. 

Benzol  has  remarkable  solvent  properties  for  many 
things  which  contain  water,  such  as  a  number  of  the 
soaps,  and  is  therefore  invaluable  to  the  paint  manu- 
facturer when  used  in  small  quantities,  for  it  prevents  the 
livering  or  saponification  of  many  of  the  paints  which  have 
alkaline  tendencies,  and  which  would  become  unfit  for 
use  if  it  were  not  for  the  small  quantity  of  benzol 
added. 

The  addition  of  benzol  to  mixed  paints  to  be  used 
for  priming  purposes  has  been  found  to  be  very  advan- 
tageous, on  account  of  the  fact  that  a  firmer  bond  is 
formed  between  a  priming  coat  and  the  wood,  so  that 
when  benzol  is  found  in  a  mixed  paint  recommended  for 
priming  purposes  it  must  be  looked  upon  as  a  valuable 
ingredient. 

The  addition  of  a  very  small  percentage  of  benzol  to 
mixed  paints  does  no  harm,  but  if  a  paint  made  with 
benzol  and  intended  as  a  priming  coat  be  used  as  a 
finishing  coat  it  is  quite  likely  to  attack  the  ground  coats 
and  produce  a  shriveled  effect. 


TURPENTINE  SUBSTITUTES  245 

The  theoretical  chemist  will  sometimes  make  a  mistake 
when  he  finds  benzol  in  a  black  mixed  paint  by  reporting 
the  presence  of  coal  tar,  from  the  false  reasoning  that  if 
benzol  is  present  coal  tar  must  be  present,  because  benzol 
is  a  constituent  of  coal  tar.  A  chemist  must,  therefore, 
be  very  careful  in  drawing  such  a  conclusion,  for  the 
presence  of  either  coal  or  pine  tar  in  a  paint  can  be 
determined  by  other  methods. 


TOLUOL 
Formula,   CeHv 

Toluol  is  very  closely  related  to  benzol,  has  practically 
the  same  specific  gravity  but  a  trifle  lower  —  .869  to  .87  — 
a  freezing  point  of  30°  F.,  and  a  boiling  point  of  230°. 
It  does  not  flash  at  air  temperature,  and  therefore 
is  of  considerable  value  where  high  flash  paints  are 
wanted. 

In  the  manufacture  of  turpentine  substitutes  out  of 
paraffin  or  petroleum  naphthas  the  addition  of  toluol  is 
of  great  value,  particularly  where  refractory  gums  are 
to  be  dissolved.  As  for  instance,  cold  petroleum  naph- 
tha added  to  a  manila  varnish  will  practically  throw  it 
out  or  precipitate  it  out,  whereas  the  addition  of  toluol 
prevents  this,  depending  upon  the  amount  of  toluol  that 
the  solvent  contains. 

It  has  been  recommended,  and  from  experiments  made 
it  appears  to  be  a  fact,  that  toluol  added  to  a  paint  in  a 
quantity  not  over  10  per  cent  is  of  great  value  in  the 
painting  of  cypress  wood,  but  it  is  doubtful  whether  it 
is  any  better  than  pine  oil,  which  can  be  used  more 
liberally  and  which  has  even  more  penetrative  effects 
and  a  higher  flash  point  than  toluol. 


246  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

XYLOL 
Formula,   CeHXCHs)? 

Xylol  really  consists  of  three  isomers  having  boiling 
points  of  278°  and  287°  respectively.  It  cannot  be  very 
well  separated  by  distillation.  Xylol  has  all  the  char- 
acteristics of  toluol  but  is  not  used  to  any  great  extent 
in  the  paint  industry  on  account  of  its  high  price. 

SOLVENT  NAPHTHA 

This  is  a  mixture  of  different  hydrocarbon  compounds 
which  have  not  yet  been  very  well  worked  out;  but  sol- 
vent naphtha  has  a  very  disagreeable  odor,  which  no 
one  has  been  able  to  remove  up  to  the  present  time,  and 
therefore  its  use  in  the  paint  industry  is  very  limited. 
When  someone  will  discover  a  method  for  deodorizing 
solvent  naphtha  it  probably  will  replace  many  of  our 
solvents,  as  it  is  really  a  better  solvent  than  anything  we 
know  of  at  present,  and  even  dissolves  such  materials 
as  gutta  percha,  balatta  and  many  forms  of  rubber. 
Its  specific  gravity  is  the  same  as  that  of  xylol  and  toluol, 
but  it  boils  at  a  much  higher  temperature,  depending 
upon  its  composition,  from  300°  F.  to  360°. 


CHAPTER  XXI 

COBALT  DRIERS l 

THE  cobalt  compounds  which  are  generally  offered  on 
the  market  today  may  be  divided  into  two  classes.  In 
the  first  are  cobaltous  oxid,  acetate,  sulphate,  chloride, 
nitrate,  hydroxid,  and  basic  carbonate.  In  the  second 
class  are  various  grades  and  qualities  of  resinates  (some- 
times called  sylvinates),  both  fused  and  precipitated, 
oleates  or  linoleates,  oleo-resinates,  tungates  and  resino- 
tungates,  besides  some  other  liquid  preparations  com- 
posed in  whole  or  part  of  the  foregoing. 

From  the  varnish  manufacturer's  standpoint  the 
substances  in  the  first  division  are  crude  materials  which 
are  utilized  in  the  production  of  the  compounds  in  the 
second  class,  and  also  in  the  preparation  of  some  var- 
nishes, liquid  driers,  drying  oils,  and  the  so-called  paint 
oils.  The  materials  enumerated  under  the  second  class 
are  the  result  of  a  varnish  maker's  labor,  and  when 
properly  made  and  used  in  mixtures  to  which  they  are 
adapted  give  very  good  results. 

The  inorganic  salts  of  cobalt  do  not  directly  come 
under  the  scope  of  this  paper,  and  thus  will  not  be 
directly  considered  except  inasmuch  as  their  use  as  crude 
material  affects  the  driers  into  whose  composition  they 
enter. 

It  is  only  within  the  past  three  years  that  the  cobalt 
driers  have  been  offered  to  the  American  paint  and  varnish 

1  By  V.  P.  Krauss,  8th  Int.  Congress  of  Applied  Chem.  From 
the  laboratory  of  Toch  Brothers,  under  the  direction  of  the  author. 

247 


248  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

manufacturers.  Up  to  the  present  time  their  use  is  not 
general,  first,  because  of  the  very  high  price,  and  second, 
because  their  use  is  not  thoroughly  understood.  Many 
experimenters  have  had  unsatisfactory  results  and  there- 
fore refused  to  further  consider  the  introduction  of 
the  new  material.  Furthermore,  not  all  of  the  cobalt 
driers,  whether  liquid,  paste,  or  solid,  now  offered  for 
sale,  are  properly  made  and  truly  adapted  to  the  pur- 
poses for  which  they  are  recommended.  This  situation, 
in  addition  to  unsatisfactory  results  obtained  by  some 
of  those  experimenting,  would  naturally  have  a  retarding 
effect  on  the  introduction  of  a  new  type  of  material. 

The  salts  of  cobalt  which  are  at  our  disposal  in  com- 
mercial quantities  are  all  of  the  cobaltous  or  divalent 
type.  It  has  been  found  that  although  they  can  be 
readily  used  in  the  manufacture  of  driers  and  worked 
like  the  various  compounds  of  manganese,  lead,  zinc, 
calcium,  aluminium,  etc.,  the  organic  compounds  formed, 
which  are  the  basis  and  active  principles  of  the  so-called 
driers,  are  not  efficient  while  in  the  cobaltous  state. 
The  cobaltic  combinations,  however,  are  very  active 
driers,  and  it  is  for  the  formation  of  trivalent  cobalt 
compounds  that  we  strive  in  the  making  of  driers.  This 
transformation  can  be  effected  in  several  ways.  By  blow- 
ing cold,  heated,  or  ozonized  air  through  the  hot  cobal- 
tous drier  stock,  or  by  the  introduction  of  liquid  or  solid 
oxidizing  agents.  The  use  of  cold  or  even  heated  air  is  a 
very  long  and  tedious  operation  if  carried  out  to  the 
extent  to  which  it  is  necessary  in  order  to  get  the  maxi- 
mum strength  in  the  drier,  and  greatly  adds  to  the  cost 
of  an  already  expensive  material.  The  use  of  the  liquid 
or  solid  oxidizers  can  be  carried  out  successfully  and  in  a 
comparatively  short  time,  although  even  when  great  care  is 
exercised  the  batch  of  material  is  in  danger  of  catching  fire. 


COBALT  DRIERS  249 

Since  driers  are  used  in  a  number  of  industries  in 
which  drying  oils  form  part  of  the  material  produced, 
and  since  the  operating  methods  of  the  various  manu- 
facturers are  widely  divergent,  the  siccatives  or  driers 
adapted  to  each  will  in  many  instances  show  widely 
different  characteristics,  not  merely  in  form  but  also  in 
composition. 

Since  the  paint  manufacturer  and  also  the  practical 
painter  who  mixes  his  own  paints  from  paste  colors  and 
raw  or  treated  oil  are  the  principal  consumers  of  what 
are  generally  known  as  driers,  the  materials  adapted  for 
their  use  may  be  first  considered.  The  driers  will,  in 
practically  all  instances,  be  in  the  liquid  state  either  very 
fluid,  of  heavy  consistency  or  of  a  semi-paste  nature. 
In  composition,  they  will  mostly  consist  of  resinates, 
tungates,  oleates,  or  linoleates,  or  combinations  of  the 
ffTfecT  .bor  trie  drying  of  linseed  oil,  when  the  proper 
driers  are  selected,  little  or  nothing  can  be  asked  in  ad- 
dition to  those  known  at  present.  When  the  general  lead, 
manganese  and  other  prevalent  metallic  driers  are  well 
chosen  raw  linseed  oil  can  without  any  difficulty  be  made 
to  dry  by  the  addition  of  from  5  to  10  per  cent  or  even 
less,  the  time  of  drying  under  average  weather  conditions 
being  from  10  to  24  hours.  By  the  use  of  cobalt  driers, 
the  same  drying  effect  can  be  obtained  when  only  from  i 
to  3  per  cent  of  a  liquid  drier  is  used.  The  author  is  not  yet 
prepared  to  say  positively  what  the  ultimate  effect  of  cobalt 
driers  is  upon  paint  films,  but  from  the  experiments  made 
it  is  deduced  that  cobalt  has  not  the  harmful  progressive 
oxidizing  action  that  some  of  the  usual  manganese-lead 
compounds  have.  It  has  also  been  noticed  that  although 
a  cobalt  drier  may  be  fairly  dark  in  color,  it  will  not  have 
as  darkening  an  effect  as  one  of  the  usual  driers  of  like 
color  would  have  upon  a  white  paint.  The  cobalt  driers 


250  CHEMISTRY  AND   TECHNOLOGY  OF      PAINTS 

likewise  show  the  same  phenomena  as  some  of  the 
others  when  used  in  excessive  amount;  that  is,  that 
although  the  paint  film  will  set  up  well  in  the  usual  time 
the  drying  action  apparently  reverses  and  the  film  remains 
tacky. 

The  terms  applied  to  liquid  driers  are  often  uncer- 
tain and  apt  to  be  misleading.  There  are  no  general 
standards  for  strength  or  consistency,  and,  it  must  be 
admitted,  many  of  the  materials  found  on  the  market 
contain  more  volatile  thinners  than  is  conducive  to 
obtaining  a  maximum  drying  effect  with  a  minimum 
quantity  of  drier. 

The  value  of  the  cobalt  specialties  depends  not  on 
their  power  to  dry  linseed  oil,  but  on  their  ability  to 
make  the  lower  priced  semi-drying  oils  act  like  it. 

Soya,  fish,  and  even  corn  and  cottonseed  oil  are 
adaptable  for  use  in  paint,  and  when  correctly  treated, 
increase  its  durability. 

In  the  making  of  waterproof  fabrics,  insulating  coat- 
ings, etc.,  both  liquid  and  solid  driers  are  used.  In  the 
linoleum,  oilcloth,  patent  leather,  artificial  leather  and 
similar  industries,  the  semi-liquid,  paste,  and  solid  driers 
are  in  demand  since  for  these  products  the  manufactur- 
ers cook  the  oils  and  varnishes  in  their  own  factories. 

The  paste  and  solid  driers  must  essentially  be  con- 
sidered under  the  caption  of  crude  materials  because 
they  must  be  churned  or  cooked  in  the  oils  or  varnishes 
in  which  they  are  used. 

The  methods  of  making  both  the  solid  and  liquid 
driers  are  in  general  similar  in  the  first  stage  of  the 
process,  and  thus  may  be  described  under  the  same 
headings. 

Resinate  of  Cobalt;  Precipitated  and  Fused.  -  -  This  is 
correctly  made  by  saponifying  rosin  or  colophony  with 


COBALT  DRIERS  251 

caustic  soda  or  sodium  carbonate,  care  being  taken  to 
avoid  an  excess  of  the  reagent,  and  then  precipitating 
with  a  solution  of  some  salt  of  cobalt.  The  chloride  or 
sulphate  serve  best  for  this  purpose.  The  precipitated 
resinate,  or  as  it  is  sometimes  called,  rosinate  or  sylvin- 
ate,  must  then  be  thoroughly  washed,  and  then  pressed 
and  dried.  This  will  yield  a  pinkish,  fairly  fluffy  powder 
when  ground,  which  will  readily  dissolve  in  oil  at  a  low 
temperature.  The  fused  variety  is  made  by  melting  the 
dried  resinate  in  a  kettle  and  then  pouring  into  cooling 
pans.  The  operation  is  performed  more  rapidly  by 
taking  the  cakes  from  the  presses  and  driving  off  the 
water  and  fusing  in  one  operation. 

Cobalt  Oleates  or  Linoleates. — The  basis  of  this  class 
is  generally  linseed  oil,  although  walnut,  perilla,  soya, 
and  some  other  oils  may  be  used.  The  oil  is  thoroughly 
saponified  with  caustic  soda,  and,  like  the  resinate,  pre- 
cipitated with  a  salt  of  cobalt.  The  material  is  then 
carefully  washed  and  pressed.  It  may  be  melted  to  form 
a  dark  viscous  heavy  fluid. 

Several  samples  of  cobalt  linoleate  examined 
consisted  of  bodied  linseed  in  which  small  amounts 
of  inorganic  cobalt  salts  had  been  dissolved.  Another 
was  of  the  same  order  with  the  addition  of  volatile 
solvents. 

True  linoleate  of  cobalt,  when  fused  with  varnish 
gums  and  dissolved  in  volatile  oils,  yields  an  excellent 
drier. 

Oleo-resinates.  -  -  This  type  of  drier  is  made  by  melting 
together  the  precipitated  resinate  and  linoleate,  some- 
times with  the  further  addition  of  fused  fossil  gum- 
resins. 

Tungate  of  Cobalt.  —  Like  the  linoleates,  the  tungate 
of  cobalt  is  made  by  saponifying  pure  China  wood  oil 


252  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

(tung  oil)  with  caustic  soda,  care  being  taken  to  avoid 
excess  of  caustic,  and  then  precipitating  with  a.  salt  of 
cobalt.  The  tungate  is  then  washed  thoroughly,  pressed 
and  generally  dried  and  fused.  Great  care  is  necessary 
in  the  preparation  of  a  tungate  since  it  oxidizes  very 
rapidly,  and  the  oxidized  material  is  useless. 

Like  the  linoleate  of  cobalt,  the  tungate  may  be  fused 
with  the  resinate  to  form  what  may  be  called  a  resino- 
tungate. 

In  general  the  foregoing  substances  are  incorporated 
in  oils  by  means  of  heat,  the  combining  temperature  be- 
ing between  300°  and  500°  F.  The  amount  necessary  will 
vary  from  about  |  per  cent  to  5  per  cent.  In  order  to  make 
liquid  driers,  the  paste  or  solid  driers  can  be  melted  alone 
or  in  combination  with  gum-resins,  bodied  linseed  oil,  or 
both,  and  then  thinned  to  liquid  consistency  with  volatile 
oils. 

Among  other  cobalt  salts,  some  of  the  chemical  manu- 
facturers offer  the  acetate,  with  directions  for  its  use  as  a 
drier.  All  agree  that  between  two  and  four  tenths  of  i 
per  cent  are  necessary  to  dry  linseed  oil.  The  oil  should 
be  at  a  temperature  between  300°  and  400°  F.,  and  be 
carefully  stirred  until  all  the  salt  is  dissolved.  Soya  and 
China  wood  oil  may  be  similarly  manipulated. 

It  is  still  a  little  too  soon  to  make  a  positive  state- 
ment as  to  how  oils  thus  treated  with  the  acetate  with- 
stand wear  and  exposure. 

Cobalt  oxide,  like  the  acetate,  can  be  directly  added 
to  oil  during  boiling.  It,  however,  dissolves  slowly  and 
necessitates  heating  to  high  temperature;  the  resulting 
product  is  also  very  dark,  and  mostly  consists  only  of 
bodied  oil.  Rosin  also  will  directly  combine  with  cobalt 
compounds  on  heating  together  in  a  suitable  kettle  or 
container.  The  product  possesses  a  number  of  objec- 


COBALT  DRIERS  253 

tionable  features.  It  still  is  mostly  unchanged  rosin, 
has  become  much  darker  and  lost  considerably  in  weight 
due  to  volatilization.  The  effect  on  oils  of  quite  a  number 
of  cobalt  compounds  was  tried,  but  none  equal  in  efficiency 
to  those  described  in  the  foregoing  was  found. 


CHAPTER  XXII 

COMBINING    MEDIUMS    AND    WATER 
COMBINING  MEDIUMS 

IN  certain  classes  of  mixed  paints,  particularly  house 
paints  which  are  made  of  corroded  lead,  sublimed  lead, 
barium  sulphate,  etc.,  there  is  a  likelihood  or  tendency  of 
the  pigment  to  settle.  This  is  more  marked  in  the  case 
of  corroded  lead  than  in  any  of  the  other  pigments.  To 
prevent  this,  in  a  measure,  water  is  added,  and  up  to  a 
certain  percentage  (i  per  cent)  both  the  manufacturer  and 
the  consumer  have  accepted  the  fact  that  water  is  not 
injurious  when  added  for  the  purpose  of  combining  the 
paint;  but  beyond  this  percentage  its  effect  is  likely  to  be 
injurious. 

Sometimes  for  the  sake  of  an  argument,  but  more 
often  for  the  sake  of  making  a  paint  which  contains  no 
more  water  than  the  natural  moisture  of  its  constituents, 
a  manufacturer  feels  the  necessity  of  adding  a  combining 
medium  other  than  water  to  prevent  the  paint  from 
settling  hard  in  the  package.  Among  these  are  gutta- 
percha  solutions,  solutions  of  balata,  para-rubber,  gum 
chicle,  etc.  The  rubber  solutions  mentioned  serve  their 
purpose  very  well  without  injuring  the  paint,  and  the 
percentage  used  is  so  small  that  it  may  be  considered 
negligible.  This,  however,  is  not  true  of  many  of  the 
mixing  varnishes  which  are  made  by  varnish  manufactur- 
ers who  have  no  experience  in  the  manufacture  of  paint. 
They  sell  rosin  varnishes  neutralized  with  lime,  lead,  or 

254 


COMBINING  MEDIUMS  AND  WATER  255 

manganese,  and  while  they  assist  very  well  in  combining 
the  lead  with  the  oil,  the  wearing  quality  of  the  paint  is 
proportionately  reduced. 

Within  the  last  few  years  a  new  combining  medium 
has  appeared  on  the  market  which  in  itself  is  an  improve- 
ment on  all  paints.  It  is  made  by  melting  a  mixture  of 
a  resin  (free  from  rosin  or  colophony)  and  heavy  linseed 
oil,  and  reducing  with  China  wood  oil  and  naphtha. 
Where  a  manufacturer  uses  a  combining  medium  of  this 
character  the  paint  becomes  more  viscous  as  it  grows 
older,  and  when  it  dries  it  produces  a  satin-like  gloss  and 

shows  fewer  brush  marks  than  a  paint  containing  water. 

< 

WATER  IN  THE  COMPOSITION  OF  MIXED  PAINTS 

The  question  of  how  much  water  shall  be  added  to 
mixed  paints,  or  how  much  water  mixed  paints  shall 
contain,  either  added  or  incidental,  is  not  fully  decided 
upon,  as  there  is  a  difference  of  opinion  as  to  its  value, 
and  likewise  a  difference  of  opinion  as  to  the  amount 
necessary  for  certain  purposes.  There  are  some  paints  in 
which  as  high  as  2  per  cent  of  water  is  necessary,  and  in 
other  paints  less  than  i  per  cent  is  purposely  added. 
That  water  is  of  great  benefit  in  certain  paints  cannot 
be  disputed,  one  large  railway  corporation  permitting 
the  addition  of  i  per  cent  of  water  to  its  mixed  and 
paste  paints. 

A  chemist  in  making  an  examination  of  a  mixed  paint 
must  necessarily  be  careful  in  giving  an  opinion  as  to  the 
amount  of  water  in  the  paint,  and  great  judgment  must 
be  used  in  a  report.  For  instance,  a  paint,  made  accord- 
ing to  a  certain  specification,  containing  a  large  mixture 
of  Venetian  red  and  yellow  ochre,  might  contain  very 
nearly  2  per  cent  of  moisture,  which  was  a  part  of  the 


256  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

composition  of  the  pigment.  Then  again,  linseed  oil  fre- 
quently contains  more  than  a  trace  of  water,  which  the 
manufacturer  cannot  extract  nor  can  he  afford  the  time 
necessary  to  allow  the  water  to  settle  out  of  the  oil.  A 
mixed  paint  should  not  contain  over  i  per  cent  of  water, 
for  it  is  unnecessary  to  add  more  than  this  amount  to 
any  paint. 

The  proper  benefits  derived  from  the  addition  of  water 
to  a  pure  linseed  oil  paint  are  suspension  of  the  pigment 
and  improvement  in  its  working  quality.  Take  the  case 
of  artists'  tube  colors  which  lie  on  the  dealers'  shelves 
for  years  and  which  are  prone  to  get  hard  and  likely 
to  separate  so  completely  that  the  color  will  be  found 
on  one  side  of  the  tube  and  the  oil  be  entirely  free  on  the 
other.  Water  is  an  absolute  necessity  in  this  case  and  is 
an  improvement  for  both  seller  and  user.  The  colors 
made  with  the  correct  addition  of  water  are  known 
to  "pile,"  and  artists  prefer  a  color  which  "piles" 
properly. 

There  are  many  ways  of  adding  water  to  a  paint. 
In  some  instances  the  required  amount  of  water,  together 
with  the  oil  and  the  drier,  are  placed  in  a  churn  or  mixer 
and  the  paste  paint  stirred  in.  Where  materials  like 
calcium  sulphate,  calcium  carbonate,  ochre,  Venetian  red, 
s'licate  of  magnesia,  silicate  of  alumina,  white  lead,  etc., 
are  used,  there  is  no  necessity  for  adding  any  combining 
material  which  will  form  a  soap  with  the  linseed  oil, 
there  being  sufficient  action  between  these  materials  and 
the  water.  It  is  an  additional  advantage  that  there  is 
less  likely  to  be  complete  saponification  in  a  mixed  paint 
to  which  no  "emulsifier"  has  been  added. 

The  following  materials  are  used  for  emulsifying 
paints: 


COMBINING  MEDIUMS  AND  WATER  257 

Saturated  solutions  of  hypochlorite  of  lime. 

Five  per  cent  solution  of  carbonate  of  soda. 

One- quarter  of  one  per  cent  solution  caustic  soda. 

One  per  cent  solution  of  carbonate  of  potash. 

Emulsion  mixtures  of  half  water  and  half  pine  oil. 

Solutions  of  hypochlorite  of  lime  containing  twenty  per  cent 

wood  alcohol. 

Ten  per  cent  solution  of  borax. 
Five  per  cent  solution  zinc  sulphate. 

Seven  per  cent  solution  lead  acetate.  • 

Five  per  cent  solution  manganese  sulphate. 
Solutions  of  ordinary  laundry  soap  or  rosin  soap  in  half 

alcohol  and  half  water. 

Weak  solutions  of  casein  dissolved  in  ammonia  water. 
Ordinary  lime  water  emulsified  with  linseed  oil. 

There  is  no  license  whatever  for  the  addition  of  much 
water  to  paint.  Some  authorities  state  that  as  high  as  i| 
per  cent  is  permissible,  but  the  author  does  not  by  any 
means  subscribe  to  that,  as  i|  gallons  of  water  in  100 
gallons  of  paint  are  far  in  excess  of  any  desirable  amount. 
Three-quarters  of  i  per  cent  or  at  most  i  per  cent 
would  probably  be  a  maximum,  and  as  an  explanation 
of  this  it  must  be  understood  that  materials  like  ochre, 
clay,  silicate  of  magnesia,  white  lead,  calcium  sulphate 
and  many  of  the  pigments  which  contain  moisture  or 
water  of  crystallization  may  carry  a  small  amount  of 
water  into  paint. 

Yet  there  may  be  cases  where  water  is  permissible  up 
to  5  per  cent,  but  only  for  interior  purposes.  Flat  wall 
paints  which  have  a  tendency  to  settle  hard  can  be 
emulsified  so  as  to  prevent  them  from  settling,  and  in  a 
case  of  this  kind  where  the  wear  of  the  paint  is  not  taken 
into  consideration  there  may  be  some  excuse  or  license 
for  the  addition  of  water. 


258  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

To  detect  water  in  paint,  particularly  in  light-colored 
paints,  is  a  comparatively  simple  matter.  The  method 
devised  by  the  author  is  almost  quantitative  for  some 
purposes.  The  first  method  ever  published  by  the 
author  consisted  in  placing  a  strip  of  gelatin  in  a  mixed 
paint.  When  a  measured  or  weighed  amount  of  mixed 
paint  was  taken  and  the  strip  of  gelatin  allowed  to  remain 
immersed  for  twenty-four  hours  a  fairly  correct  quantita- 
tive determination  was  obtained.  Another  method  de- 
scribed some  years  ago  involved  the  use  of  anhydrous 
sulphate  of  copper,  a  bluish  white  powder,  which  on  the 
addition  of  water  returns  to  the  natural  dark  blue  color 
of  crystallized  copper  sulphate. 

The  author  has,  however,  devised  the  scheme  of 
using  a  glass  plate  and  mixing  a  paint  with  a  dyestuff 
such  as  "Erythrosine  B."  When  about  J  gram  of  the 
dye  and  5  grams  of  mixed  paint  are  rubbed  together 
with  a  palette  knife  on  a  sheet  of  glass,  a  paint  con- 
taining no  water  will  produce  a  distinct  pearl-gray  color; 
if  there  is  water  in  the  paint  the  mixture  changes  almost 
immediately  to  a  brilliant  cerise  red,  and  if  there  is  much 
water  in  the  paint  (over  2  per  cent)  the  color  changes 
into  a  crimson,  so  that  the  reaction  is  clearly  marked. 
The  test  must  not  be  allowed  to  stand  more  than  four 
minutes,  since  even  paints  which  contain  no  added  water 
but  which  naturally  contain  traces  of  moisture  will  begin 
to  change  into  a  rosy  color,  in  which  the  presence  cannot 
be  reported.  In  red,  black  or  dark  colored  paints  Ery- 
throsine B  is  just  as  indicative  of  water  in  paint,  par- 
ticularly when  the  mixture  is  viewed  by  transmitted  light. 
Even  in  the  case  of  black  paint  the  erythrosine  emulsion 
paint  will  produce  a  beautiful  purple  color. 


CHAPTER   XXIII 
FINE  GRINDING 

THERE  is  a  great  difference  of  opinion  on  the  question 
of  how  paints  should  be  ground,  and  a  careful  canvas  on 
this  subject  reveals  the  fact  that  most  paint  manu- 
facturers believe  that  all  paints  should  be  very  finely 
ground.  This  is  a  great  error,  for  there  are  many  con- 
ditions where  a  paint  should  be  slightly  coarse  in  order 
to  give  proper  results,  for  if  paints  do  not  have  a  slight 
amount  of  coarseness,  or  "tooth"  as  it  is  called,  one  coat 
will  not  hold  successfully  on  the  other,  and  it  is  for  the 
very  reason  of  producing  a  mechanical  bond  that  fillers 
are  used  which  have  a  distinct  grain.  Without  making 
any  general  rule  on  the  subject,  all  priming  coats  should 
have  sufficient  tooth  to  enable  the  succeeding  coat  to 
hold. 

Those  familiar  with  the  subject  are  aware  of  the 
fact  that  a  gloss  coat  on  a  gloss  coat  very  frequently 
peels,  and  the  same  is  sometimes  true  of  a  gloss  coat  on  a 
priming  coat  which  is  too  finely  ground.  This  does  not 
apply  to  a  finishing  coat,  because  the  finer  a  finishing 
coat  the  longer  it  lasts  and  the  cleaner  it  remains,  for  a 
coarse  finishing  coat  will  hold  dust  and  dirt  which  even  a 
heavy  rainstorm  will  not  always  dislodge,  while  a  smooth, 
finely  ground  finishing  coat  acts  like  a  glaze  and  remains 
clean  until  it  perishes.  It  may  therefore  be  taken  as  a 
general  statement  that  priming  coats  should  be  slightly 
coarse  and  finishing  coats  should  always  be  fine. 

259 


260  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

If  you  take  the  case  of  the  finishing  of  a  very  fine 
object  like  a  piano  or  an  automobile,  rubbing  varnishes 
are  used  on  the  undercoat,  and  these  varnishes  are 
scarified  with  pumice  stone  for  two  reasons:  first,  so  as 
to  smooth  the  coat  thoroughly  because  the  succeeding 
coat  when  applied  will  then  itself  produce  a  smooth  and 
glossy  effect,  and  secondly,  so  that  the  next  coat  which 
is  applied  can  bind  itself  mechanically  to  the  undercoat. 
If,  therefore,  rubbing  is  a  practice  where  varnished  objects 
are  to  be  finished,  it  must  be  taken  as  a  rule  that  where 
paints  are  applied  and  rubbing  is  not  practiced  a  slight 
grain  is  of  great  benefit,  so  that  the  question  of  fine 
grinding  does  not  apply  to  every  case. 


CHAPTER   XXIV 

THE  INFLUENCE  or  SUNLIGHT  ON  PAINTS  AND 
VARNISHES  l 

IT  may  properly  be  said  that  direct  sunlight  has  a 
very  destructive  action  on  paint  and  varnish  films,  and 
the  author  had  noted  as  far  back  as  15  years  ago  that 
many  of  the  paint  materials  that  were  perfectly  water- 
proof in  places  where  sunlight  never  reached  became 
permeable  to  water  and  disintegrated  very  rapidly  when 
exposed  to  direct  sunlight.  As  an  example  of  this,  it 
might  be  cited  that  pure  asphaltum,  when  applied  in  a 
good  continuous  coat  on  cast  iron  pipes  in  a  cellar,  will 
last  from  three  to  four  years,  yet  the  same  asphaltum 
when  applied  on  the  roof  of  a  building  will  show  al- 
most complete  decomposition  within  20  days.  In  order, 
therefore,  to  determine  the  cause,  the  first  experiments 
with  a  series  of  bitumens  were  made  as  follows:  Sheets 
of  clean  steel  and  wood  were  painted  with  a  variety  of 
bitumen  compounds  and  exposed  to  direct  sunlight  under 
various  colored  glasses,  finally  reduced  to  the  three 
colors,  violet,  green,  and  red;  for  obvious  reasons  these 
three  served  all  purposes.  It  was  found  at  the  end  of 
four  weeks  that  the  bitumens  exposed  under  the  blue 
rays  showed  marked  signs  of  decomposition,  those  under 
the  green  showed  some  signs,  and  those  under  the  red 
none  whatever.  The  same  experiments  were  tried  again 
by  cementing  the  glass  to  the  painted  surface,  when 
little  or  no  decomposition  followed  in  any  case.  A  large 

1  Reprinted  from  the  Journal  of  the  Society  of  Chemical  Industry, 
April  15,  1908.  No.  7,  Vol.  XXVII,  Maximilian  Toch. 

261 


262  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

variety  of  experiments  was  then  tried  by  mixing  the 
bitumens  with  various  pigments,  and  a  preservative 
action  was  obtained  in  direct  ratio  to  the  pigment  used, 
so  much  so  that  a  sample  of  paint  made  to  contain  80 
per  cent  of  bitumen,  15  per  cent  of  linseed  oil,  and  5  per 
cent  of  finely  divided  carbon,  showed  only  slight  deterio- 
ration at  the  end  of  six  months;  this  was  easily  accounted 
for  by  the  fact  that  the  finely  divided  carbon  prevented 
the  absorption  of  many  actinic  rays.  While  these 
experiments  were  very  conclusive,  it  was  necessary  to 
determine  the  cause,  and  to  this  end  a  large  variety  of 
experiments  was  conducted,  all  of  which  were  productive 
of  excellent  results. 

All  asphaltums  are  bitumens,  but  all  bitumens  are 
not  asphaltums,.  and  it  is  necessary  to  look  into  the  com- 
position of  the  asphaltums  which  decompose  in  the  sun- 
light and  of  those  resins  which  do  not.  The  difference 
between  a  resin  and  an  asphaltic  bitumen  may  generally 
be  stated  as  follows :  —  Asphaltums  and  bitumens  are 
composed  principally  of  carbon  and  hydrogen,  whereas 
the  resins  are  semi-fossilized,  and  composed  of  carbon, 
hydrogen,  and  oxygen.  Asphaltums,  whether  they  be 
natural  or  artificial,  consist  largely  of  hydrocarbons  of 
the  series  of  CnH2n-2,  CnH2n-4,  CnH2n-8,  etc.,  and  according 
to  Clifford  Richardson  1  and  others,  these  hydrocarbons 
are  probably  polymethylenes.  From  a  large  number  of 
combustion  determinations  made  with  bitumens,  it  may 
be  safely  stated  that  many  of  the  bitumens  are  probably 
polymethylenes  of  various  series,  as  above.  There  are, 
of  course,  substances  in  bitumens  such  as  sulphur  and 
nitrogen,  which  probably  exert  very  little  influence  on 
the  material  from  an  actinic  point  of  view.  Assuming, 

1  See  "  The  Modern  Asphalt  Pavement "  and  "  Origin  of  Asphalt," 
by  Clifford  Richardson. 


INFLUENCE  OF  SUNLIGHT  ON  PAINTS  AND   VARNISHES      263 

therefore,  that  the  hydrocarbons  are  of  the  character 
described,  we  should  have  under  the  combined  action 
of  the  oxygen  of  the  air  and  the  actinic  rays  of  the  light, 
sometimes,  in  conjunction  with  moisture,  a  favorable 
condition  where  oxygen  would  combine  with  hydrogen, 
and  carbon  be  set  free.  Therefore,  if  this  reaction  takes 
place,  all  bitumens  in  a  short  time  ought  to  become  car- 
bonized and  deposit  relatively  pure  carbon  on  their  sur- 
faces, and  this  is  exactly  what  takes  place,  the  action  of 
the  sunlight  probably  resulting  in  a  combination  of  the 
hydrogen  with  oxygen,  and  a  deposit  of  what  appears  to 
be  carbon  takes  place.  If  this,  then,  is  the  first  lucid 
explanation  of  the  decomposition  of  bitumens  in  sunlight, 
it  is  the  explanation  of  the  cause  of  the  valuelessness  of 
pure  bitumens  as  protective  paints  for  exterior  purposes. 
Even  the  addition  of  a  small  amount  of  bitumen  to  a 
large  percentage  of  otherwise  good  paint  will  result  in  the 
decomposition  of  this  paint  when  exposed  to  the  direct 
action  of  moisture  and  light. 

We  have  no  such  action  when  materials  are  used  which 
are  glycerides  of  fatty  acids,  such  as  fish  oil,  Chinese 
wood  oil,  and  linseed  oil.  Indeed,  any  one  of  these  three 
oils  are  light-proof  in  a  very  large  degree,  and  fish  oil 
and  Chinese  wood  oil  are  both  heat-proof  and  light-proof. 
Linseed  oil,  however,  unless  prepared  with  fossil  resins, 
is  not  water-proof,  but  fish  oil  is  more  water-proof,  and 
Chinese  wood  oil  most  water-proof  of  all.  At  the  same 
time,  pure  Chinese  wood  oil  is  less  light-proof,  next  comes 
fish  oil,  while  linseed  oil  is  most  light-proof,  and  there 
would  appear  to  be  an  established  ratio  that  a  paint  or 
varnish  containing  the  least  amount  of  oxygen  is  the 
least  light-proof  and  the  most  water-proof,  and  the  paint 
containing  the  largest  amount  of  oxygen  is  most  proof 
against  light,  and  least  water-proof. 


264  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

In  conclusion,  and  as  evidence  of  the  correctness  of 
these  statements,  if  a  sheet  of  metal  or  wood  be  painted 
with  asphaltum  or  bitumen-paint  and  exposed  to  sunlight 
and  air,  the  coating  will  be  rapidly  decomposed,  and  after 
a  lapse  of  20  days  probably  carbon  will  be  set  free. 
At  least,  this  is  a  deduction  from  the  nature  of  the 
bitumens.  Minute  scrapings  from  the  surface  of  exposed 
bitumens  show  that  the  principal  constituent  is  carbon, 
and,  whereas  the  original  material  contains  much  less, 
the  exposed  bitumen  shows  over  95  per  cent  of  carbon, 
the  remainder  being  principally  hydrogen,  with  a  small 
difference,  which  is  evidently  oxygen.  This  shows  that 
the  general  reaction  tends  to  produce  carbon. 

The  painting  of  concrete  to  preserve  it  against  the 
action  of  moisture  and  frost  is  destined  to  become  as  large 
an  industry  as  the  painting  of  wood,  and  those  who  have 
tried  asphaltum  paints  for  this  purpose  have  already 
found  to  their  sorrow  that  disintegration  takes  place  in 
a  very  short  time,  even  though  the  material  be  perfectly 
proof  against  the  alkaline  action  of  the  lime  in  the  con- 
crete, and  as  linseed  oil  paint  is  rapidly  destroyed  by 
concrete  itself,  owing  to  the  interaction  of  the  lime  and 
the  linseed  oil,  we  have  to  look  for  other  materials  with 
which  we  can  coat  concrete  in  order  to  preserve  not  only 
its  appearance,  but  the  very  structure  itself. 

Regarding  the  action  of  sunlight  on  pigments,  it  is 
well  known  that  lithopone  is  rapidly  acted  upon  by  light, 
and  direct  sunlight  turns  it  a  dark  gray,  but  frequently 
overnight  the  color  leaves  it  and  it  is  brilliant  white 
again  in  the  morning.  English  vermilion  (mercuric 
sulphide)  is  also  acted  upon  by  sunlight,  and  forms  first 
a  brown  compound  and  then  a  black  compound  of  mer- 
cury. This  has  been  regarded  as  mercurous  sulphide  or 
as  a  sub-sulphide  of  mercury,  but  on  this  question  the 


INFLUENCE  OF  SUNLIGHT  ON  PAINTS  AND  VARNISHES      265 

writer  has  doubts.  Some  of  the  oxids  of  iron,  par- 
ticularly the  bright  red  ferric  oxids,  are  affected  by  light, 
and  a  compound  results  which  from  bright  red  turns  to 
brown,  probably  a  change  tending  towards  the  formation 
of  ferrous  oxid. 

We  know  that  a  large  number  of  the  organic  dyestuffs 
tend  to  bleach  in  the  sunlight,  but  sunlight  alone  is 
never  very  active  regarding  the  decomposition  of  colors 
when  air  is  excluded,  for  even  mercury  vermillion  is 
regarded  as  permanent  when  it  is  covered  by  a  coat  of 
varnish.  This  is  largely  true  of  the  organic  lakes  and 
finer  colors  used  for  coach  painting.  Linseed  oil  itself 
is  bleached  by  sunlight,  but  this  is  a  chemical  change 
produced  by  the  actinic  rays  in  which  the  green  chloro- 
phyll is  changed  to  pale  yellow. 


CHAPTER   XXV 

PAINT  VEHICLES  AS  PROTECTIVE  AGENTS  AGAINST 
CORROSION  l 

A  CAREFUL  search  of  the  literature  of  the  past  twenty 
years  has  failed  to  reveal  anything  like  a  systematic 
investigation  of  the  relative  value  of  different  vehicles 
used  in  the  manufacture  of  paints  for  structural  steel 
and  the  prevention  of  corrosion.  There  are  a  few  isolated 
cases  in  which  boiled  linseed  oil,2  Kauri  linseed  oil  var- 
nish 3  and  spar  varnish  as  protective  coatings  on  structural 
steel  were  studied.  For  many  years  past  much  has  been 
written  and  many  investigations  have  been  made  on  the 
protective  quality  of  the  pigments,  but  no  one  has  appar- 
ently made  any  study  of  the  vehicles. 

It  is  quite  obvious  that  without  a  vehicle  a  pigment  is 
useless,  and  the  author  knows  of  no  instance  where  a  pig- 
ment could  be  used  alone,  with  perhaps  the  single  exception 
of  Portland  cement,  if  that  may  be  classed  as  a  pigment; 
even  then,  Portland  cement  would  be  useless  unless  water 
were  used  as  a  vehicle.  The  example  need  hardly  be  called 
to  your  attention  of  taking  a  dry  pigment  and  using  water 
as  a  vehicle  to  show  you  that  when  the  water  evaporated 
it  would  leave  the  pigment,  and  the  pigment  in  turn 
would  leave  the  metal;  and  yet,  to  the  best  of  the  author's 

1  Journal  of  Society  of  Chemical  Industry,  June  15,  1915.      No. 
n,  Vol.  XXXIV,  by  Maximilian  Toch. 

2  C.    Von   Kreybig,   Farben  Ztg.,   17,    1766-8;    J.    N.   Friend, 
Carnegie  Scholarship  Report,  Iron  and  Steel  Inst.,  May,  1913,  pp.  1-9. 

3  Address   of   Prof.  A.  H.  Sabin   before   American    Society   of 
Civil  Engineers,  Nov.  4,  1896,  reported  in  Engineering  News,  July 
28,  1898. 

266 


PROTECTIVE    AGENTS    AGAINST    CORROSION  267 

knowledge,  nobody  has  paid  any  attention  to  the  very  im- 
portant role  that  is  played  by  the  vehicle  itself.  There  is 
an  old  proverb  which  says,  "One  hand  is  useless,  for  one 
hand  washes  the  other,"  and  it  seems  that  the  same  is 
true  with  reference  to  vehicle  and  pigment,  for  one  is  of 
little  value  without  the  other,  and  if  any  value  is  to  be 
attached  to  either  of  them  the  vehicle  has  by  far  the 
advantage,  because  there  are  some  vehicles  which  protect 
for  a  considerable  length  of  time. 

With  this  end  in  view  exposure  tests  were  made  in 
1913,  in  which  fifty- two  steel  plates  (in  duplicate)  were 
carefully  freed  from  grease  by  washing  with  benzol, 
dried,  sanded,  and  rubbed  clean  with  pumice,  and  then 
coated  with  all  the  paint  vehicles  or  protective  vehicles 
to  the  extent  of  fifty- two  in  number,  many  of  which,  of 
course,  are  seldom,  if  ever,  used  alone,  and  some  of 
which  are  failures  a  short  time  after  they  are  put  on. 
However,  the  author  wanted  to  do  this  thing  thoroughly, 
and  for  this  purpose  selected  the  same  quality  of  steel, 
known  as  cutlery  steel,  which  has  been  used  by  him  for 
many  years  for  his  exposure  tests.  It  is  a  steel  which 
rusts  very  rapidly. 

Those  plates  must  be  eliminated  which  have  shown  no 
rusting  in  the  year  and  five  months  that  they  have  been 
exposed.  These  were  coated  with  the  paraffin  or  machin- 
ery oil  compounds,  and  it  would  be  poor  advice  to  any 
engineer  to  coat  steel  with  paraffin  compounds,  for  the 
method  of  cleaning  before  the  application  of  any  good 
paint  would  have  to  be  very  carefully  followed  out, 
since  no  protective  paint  would  hold  on  steel  that  re- 
tained the  least  trace  of  a  paraffin  coat.  Then  the 
paraffin,  or  non-drying  oils,  all  collect  a  great  deal  of 
dirt,  which  showed  that  this  would  have  to  be  entirely 
removed  before  any  paint  could  be  applied. 


268  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Plate  No.  41  showed  excellent  results,  and  a  material 
of  this  kind  would  not  be  so  very  expensive  where  en- 
gineers demand  that  steel  be  coated  with  a  clear  liquid 
in  the  shop  so  that  the  steel  may  be  inspected  in  the 
field.  This  was  composed  of  half  spar  varnish  and  half 
stand  oil.  Stand  oil  is  practically  a  polymerized  linseed 
oil.  Linseed  oil  when  heated  to  550°  F.,  with  a  drier 
like  Japanner's  Prussian  brown  or  borate  of  manganese 
will  produce  a  very  thick  viscous  liquid,  which  is  largely 
used  as  a  patent  leather  finish.  This  can  be  reduced 
with  50  per  cent  of  thinner  and  still  have  the  fluid- 
ity or  viscosity  of  raw  linseed  oil,  and  is,  therefore, 
inexpensive. 

Plate  No.  50  was  coated  with  a  material  containing 
10  per  cent  of  paraffin  oil,  which  might  be  classed  as 
an  adulterated  linseed  oil,  and  while  it  showed  up  very 
well,  it  could  not  be  recommended  because  on  an  exposed 
structure  like  a  bridge  a  coat  of  good  protective  paint 
would  not  adhere  very  thoroughly. 

Plate  No.  52  has  taught  a  valuable  lesson  with  regard 
to  the  use  of  raw  China  wood  oil  which  is  heated  to  a  suf- 
ficient degree  of  heat  to  take  10  per  cent  of  a  tungate 
drier,  and  then  thinned  with  15  per  cent  of  benzine.  This 
made  a  material  which  is  hardly  more  expensive  than 
good,  boiled  linseed  oil,  and  left  a  most  excellent  surface 
for  repainting.  In  fact,  this  has  proved  itself  the  equal 
of  plates  No.  22  and  No.  23,  with  the  addition  of  a  better 
surface  for  repainting. 

Plate  No.  46  was  coated  with  kettle-boiled  linseed  oil, 
and  is  very  good,  but  this  material  might  be  regarded 
by  some  engineers  as  too  expensive  for  application,  as 
it  took  all  day  to  make  this  oil.  A  carefully  selected 
linseed  oil  was  chosen  to  start  with,  to  which  was  added 
5  per  cent  of  litharge  and  no  other  drier.  This  oil  dried 


PROTECTIVE    AGENTS    AGAINST    CORROSION  269 

very  badly,  but  when  it  did  dry  produced  a  good  flexible 
film  which  lasted.  This  must  not  be  confounded  with 
the  average  boiled  linseed  oil  of  commerce. 

The  various  coatings  used  in  these  exposure  tests 
have  been  divided  according  to  their  protective  value 
into  five  classes: 

1  and  i  b  -  -  Those  vehicles  which  have  little  or  no 
value  for  the  prevention  of  rusting. 

(a)  The  raw  and  refined  drying  and  semi-drying 
vegetable  oils.  (Plates  Nos.  i,  7,  8,  13,  35,  36,  47,  48.) 

(b}  The  same  oils  to  which  10  per  cent  of  drier 
had  been  added.  (Plates  Nos.  2,  3,  4,  6,  9,  10,  n,  12, 

14,  34-) 

(c)  The  more  or  less  volatile  paint  thinners.     (Plates 
Nos.  17,  18,  19,  20,  33.) 

(d)  Solutions  of  celluloid  and  pyroxylin.     (Plates  Nos. 
24,  25.) 

(e)  The  liquid  (at  room  temp.)  paraffin  oils.     (Plates 
Nos.  21,  30.) 

2  -  -  Those    vehicles    which    showed    some    degree    of 
protection,  though  not  very  much  at  best. 

(a)  Wood-oil  varnishes  containing  a  certain  percentage 
of  rosin.  (Plates  Nos.  26,  29.) 

(6)  Copal- wood-oil  varnishes.     (Plates  Nos.  27,  28.) 

(c)  Varnishes  made  from  linseed  oil  which  had  been 
thickened  and  oxidized  by  blowing  with  air,  oxygen  or 
ozonized  air.  (Plates  Nos.  32,  37.) 

This  compared  with  the  results  obtained  below  with 
cooked-oil  varnishes  proves  conclusively  that  the  film 
yielded  by  a  blown  oil  is  not  nearly  as  waterproof  and 
resistant  to  severe  weather  conditions  as  that  formed  by 
a  boiled  or  polymerized  oil. 

3  —  Varnishes   or   varnish   mixtures   which   protected 
the  steel  very  nicely  as  long  as  weather  conditions  were 


270  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

not  severe  and  temperature  changes  not  very  rapid  and 
pronounced.     (Plates  Nos.  39,  40,  42,  43,  44,  45,  49.) 

4  -  -  The    semi-solid    and    solid    paraffin    oils.     These 
show    a   very    high    degree    of   protection    from   rusting. 
(Plates  Nos.  15,  31.) 

5  -  -  Those    varnishes    and    vehicles    which    afford    a 
high  degree  of  protection  against  corrosion.     To  be  set 
down  in  this  class  a  material  must  be  extremely  water- 
proof; it  must  dry  with  a  film  which  is  very  elastic  and 
yet  tough  in  order  to  be  able  to  withstand  "weathering." 
A  film  which  cannot   remain   intact   against    condensed 
moisture,  snow  and  ice  and  despite  comparatively  wide 
and  sometimes  rapid  changes  in  temperature  (as  between 
day   and   night   even   in   rather   warm  climates),  will  of 
necessity   afford   very   little   protection   for   the   steel   to 
which  it  is  applied.     As  the  table  on  pages  272-273  shows, 
this  class  comprises: 

(a)  Spar  varnish.     (Plate  No.  16.) 

(b)  Varnishes  made  from  linseed  oil,  or  China  wood 
oil,  which  have  been  thickened  by  a  heat  process.    (Plates 

NOS.    22,    23,    52.) 

(c)  Open  kettle-boiled  oil.     (Plate  No.  46.) 

In  Plate  No.  50  we  find  a  rather  anomalous  case. 
It  seems  that  raw  linseed  oil  which  has  been  dried  with  a 
small  percentage  of  a  liquid  paraffin  oil  proved  to  be  an 
excellent  coating  for  rust  prevention. 

The  addition  of  any  paraffin  or  non-drying  oil,  even 
in  such  a  small  quantity  as  is  shown  in  Plate  No.  50, 
is  dangerous  in  case  repainting  becomes  necessary.  Al- 
though the  matter  is  not  settled  in  the  author's  mind  as  to 
whether  linseed  oil  and  paraffin  oil  dissolve  in  each  other, 
his  idea  at  present  is  that,  although  they  apparently  make 
a  clear  solution,  separation  takes  place.  Several  experi- 
ments were  conducted,  and  it  was  found  that  a  film  of  lin- 


PROTECTIVE  AGENTS  AGAINST  CORROSION  271 

seed  oil  which  contains  paraffin  oil  in  some  quantities  when 
apparently  dry  shows  minute  globules  of  paraffin  oil  in 
wet  condition  when  the  film  is  heated  over  100°  C.  A 
film  of  linseed  oil  containing  10  per  cent  of  paraffin  oil 
after  it  is  six  months  old  can  be  extracted  with  naphtha 
and  shows  uncombined  paraffin  oil.  These  experiments 
prove  conclusively  that  it  is  dangerous  to  mix  a  paraffin 
oil  with  linseed  oil  for  any  purpose,  excepting  where 
it  is  not  necessary,  or  not  the  intention,  to  repaint 
subsequently. 

NOTE:  All  the  photographs  submitted  (see  pages  274- 
275)  were  taken  during  December,  1914. 


272 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


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CHAPTER  XXVI 

THE  ELECTROLYTIC  CORROSION  OF  STRUCTURAL  STEEL  1 

ENGINEERS  have  commented  publicly  on  the  electro- 
lytic corrosion  of  structural  steel,  particularly  those  parts 
known  as  grillage  beams,  supporting  columns  and  base 
posts,  which  are  either  in  the  ground  or  surrounded  by 
concrete  and  partly  above  the  ground,  with  a  view  of 
determining  beyond  question  at  which  of  the  poles  corro- 
sion occurs,  and  whether  one  pole  is  more  active  than  the 
other. 

The  author  performed  an  experiment  by  taking  two 
sheets  of  high  grade  watch  spring  steel,  which  is  ex- 
tremely susceptible  to  corrosion,  and  connecting  them 
with  the  ordinary  bluestone  telegraphic  cell.  A  volt  am- 
meter was  placed  in  the  circuit  and  the  two  pieces  of  steel 
buried  up  to  5  in.  in  sand.  Careful  observation  was  made 
every  day  to  see  that  the  current  was  uniform,  and  the 
sand  was  first  moistened  with  salt  water  and  then  contin- 
ually moistened  with  distilled  water  so  that  the  same 
strength  of  salt  solution  was  maintained.  This  experi- 
ment was  conducted  for  100  days,  and  assuming  that  the 
current  travels  from  plus  to  minus,  or  from  anode  to 
cathode,  the  anode  being  connected  with  the  copper  and 
the  cathode  being  connected  with  the  zinc,  corrosion  was 
noticed  almost  immediately  at  the  anode,  and  the  plates 
showed  violent  corrosion  at  the  anode  and  practically  no 
corrosion  at  the  cathode.  These  plates  indicated  some 

1  By  Maximilian  Toch.  Reprinted  from  Proceedings  of 
American  Society  for  Testing  Materials,  Volume  VI,  1906. 

276 


ELECTROLYTIC    CORROSION    OF    STRUCTURAL    STEEL        277 

slight  corrosion  on  the  cathode,  which,  however,  was 
principally  chemical  corrosion. 

The  strength  of  the  current  was  .05  of  a  volt  and  the 
distance  between  the  plates,  varying  in  the  damp  sand, 
was  ij  inches,  and  the  amperage  varied  from  .02  to  .05. 

The  current  was  measured  by  a  "Pignolet,"  direct 
reading,  continuous  current  volt-ammeter,  and  the  amount 
of  current  which  produced  this  corrosion  was  exceptionally 
small. 

Another  experiment  was  tried  exactly  in  the  same 
manner,  for  a  shorter  period  of  time,  but  instead  of  using 
two  plates,  three  plates  were  used,  the  third  one  being 
designated  as  the  "free"  plate,  in  which  chemical  corro- 
sion had  full  sway.  At  the  end  of  six  days  these  plates 
were  removed;  the  anode  showed  marked  corrosion,  the 
cathode  plate  showing  practically  no  corrosion  at  all,  and 
the  "free"  plate  showed  a  fair  average  between  the 
cathode  and  the  anode,  and  it  can  be  deduced  that  the 
difference  between  the  cathode  and  the  anode  corrosion 
is  equal  to  the  "free"  corrosion.  In  other  words,  there 
is  many  times  more  corrosion  on  the  anode  than  there  is 
on  the  "free"  plate,  and  no  corrosion  on  the  cathode 
plate. 

The  rust  first  produced  was  the  green  ferrous  oxid, 
Fe(OH)2,  which,  being  a  very  unstable  product,  was 
quickly  converted  in  the  air  into  Fe2O3,  N(H2O). 

The  current  was  .1  of  a  volt  and  .1  of  an  ampere 
which  produced  this  result.  The  salt  solution  was  four 
times  as  strong  as  that  produced  in  the  first  experiment. 

A  third  experiment  was,  however,  of  the  greatest  im- 
portance, owing  to  the  fact  that  the  author  attempted 
to  imitate  the  conditions  exactly  as  they  existed  in 
buildings.  The  same  kind  of  steel  was  taken  and  bedded 
in  various  mixtures  of  concrete,  starting  from  neat 


278  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

cement  and  going  up  to  1:3:5.  There  is  a  well-known 
law  in  physical  chemistry  that  reactions  which  take  place 
with  an  increase  of  pressure  are  retarded  by  an  increase 
of  pressure,  and  the  question  has  come  up  as  to  whether 
it  is  possible  for  steel  to  corrode  when  surrounded  by 
concrete,  many  engineers  holding  that  the  alkaline  na- 
ture of  the  cement  will  prevent  the  corrosion,  and  others 
holding  that  in  conjunction  with  this  condition  the  pres- 
sure exerted  by  the  concrete  prevents  chemical  decom- 
position. The  author  is  glad  to  be  able  to  throw  some 
light  on  this  subject,  and  the  following  experiment  was 
carried  out: 

In  the  first  place  cement  was  taken  of  known  com- 
position, agreeing  practically  with  the  definition  as  quoted 
in  the  Journal  of  the  American  Chemical  Society,  July, 
1903,  when  the  question  of  the  permanent  protection  of 
iron  and  steel  by  means  of  cement  was  thoroughly 
gone  into.  The  cement  for  these  experiments  was 
what  might  be  termed  the  tri-calcic  silicate  and 
calcium  aluminate.  This  is  in  contradistinction  to  the 
general  classes  of  Portland  cements  containing  dicalcium 
ferrite  as  a  part  of  their  composition  and  free  calcium 
sulphate  in  excess.  A  cement  of  the  calcium  aluminate 
class,  free  from  iron  and  free  from  calcium  sulphate,  is  a 
well-known  protector  of  steel  and  iron  against  corrosion, 
and  this  class  of  cement  was  used  in  these  experiments. 
The  pieces  of  steel  were  connected  up  with  six  elementary 
cells  of  sufficiently  high  voltage  and  amperage,  and  it  was 
impossible  to  get  a  direct  reading  from  the  volt-ammeter, 
the  instrument  being  too  sensitive.  The  seven  parts  of 
cement  containing  the  steel  strips  were  then  put  into  the 
circuit  and  wet  every  few  hours  with  solutions  of  5  per 
cent  sodium  chloride  and  i  per  cent  nitric  acid,  and  water, 
in  order  to  increase  their  conductivity  and  produce  corro- 


ELECTROLYTIC    CORROSION    OF    STRUCTURAL    STEEL        279 

sion  as  rapidly  as  possible.  The  average  strength  of  the 
current  was  .05  volts  and  .05  amperes  throughout  the  entire 
experiment.  Corrosion  was  immediately  noticed  at  the 
anode  pole,  and  the  pat  of  neat  cement,  which  should  have 
protected  the  steel  most  perfectly  against  all  kinds  of  corro- 
sion, showed  a  hair  line  split  colored  with  rust  at  the  end 
of  the  third  day,  which  demonstrated  that  the  chemical 
reaction  of  rusting  had  taken  place  at  the  anode;  that  the 
molecular  increase  had  likewise  taken  place,  and  the  pres- 
sure caused  by  the  molecular  increase  had  split  the  block. 
The  steel  in  each  alternate  pat  was  painted  half  the  length 
which  was  embedded  in  the  cement  with  an  insulating 
paint  of  known  composition  having  a  voltage  resistance  of 
625  volts  per  millimeter.  The  results  obtained  after  these 
various  briquettes  were  broken  open  demonstrated  that 
electrolytic  corrosion  takes  place  most  violently  at  the 
anode  unless  the  steel  be  coated  with  an  insulating 
medium. 

Cement,  concrete,  or  even  neat  cement,  is  therefore  no 
protection  against  electrolytic  corrosion,  unless  the  steel  be 
insulated  as  heretofore  mentioned,  and  there  was  absolutely 
no  corrosion  wiiere  coated  with  insulating  material.  It 
must  be  noted  that  the  cathode  in  all  these  experiments 
was  perfectly  free  from  any  signs  of  oxidation. 

The  result  of  this  entire  series  of  experiments  is  to 
prove  conclusively  that  electrolytic  corrosion  of  struc- 
tural steel  embedded  in  concrete  or  sand  takes  place  only 
at  the  anode  and  there  with  great  violence;  and  further- 
more, that  the  cathode  is  protected  by  the  electrical  cur- 
rent. The  popular  impression  that  cement  is  a  protector 
against  all  kinds  of  corrosion  is  fallacious.  The  anode 
does  not  only  rust  very  violently,  but  a  molecular  in- 
crease of  volume  may  take  place  which  will  split  the  con- 
crete shell. 


280  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Another  conclusion  arrived  at  is  that  the  electrolytic 
rusting  of  grillage  beams  of  buildings  need  not  be  feared 
if  the  structural  steel  be  protected  by  a  good  insulating 
material,  but  the  insulating  medium  should  form  a  bond 
with  concrete. 


CHAPTER  XXVII 

PAINTERS'  HYGIENE 

ALL  paints  should  be  regarded  as  poisonous,  and  even 
though  it  may  be  understood  as  a  general  rule  that 
materials  like  ultramarine  blue  are  non-toxic  or  that 
silica  has  no  effect  upon  the  system,  it  is  unwise  for  the 
paint  manufacturer  to  permit  his  men  either  to  breathe 
these  in  dry  dust  form  or  to  allow  his  workmen  to  eat 
their  meals  before  washing  themselves  thoroughly.  We 
are  all  very  familiar  with  the  fact  that  white  lead  pro- 
duces lead  poisoning,  but  in  any  w^ell-regulated  factory 
there  is  no  excuse  for  this,  and  the  amount  of  lead 
poisoning  produced  in  factories  like  the  large  lead  manu- 
factories- in  the  United  States  is  reduced  to  a  minimum 
because  the  workmen  are  looked  after  most  thoroughly. 
Workmen  who  are  employed  in  a  dusty  atmosphere  should 
always  wear  respirators,  and  workmen  who  work  with 
lead  products  should  not  be  permitted  to  grow  mous- 
taches, as  the  dust  of  many  of  the  poisonous  pigments 
settles  in  the  moustache  and  is  then  absorbed  through 
the  nose.  White  lead  under  the  finger  nails  is  absorbed 
into  the  system,  and  a  careful  watch  of  these  things  will 
prevent  any  disease  among  the  men;  but  all  in  all  there 
is  more  sensationalism  and  hysteria  on  this  subject  than 
is  warranted  by  the  results,  for  in  paint  factories  where 
sufficient  care  is  taken  there  is  practically  no  illness 

among  the  men. 

281 


282  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Paint  vapors  are  all  toxic,  and  any  painter  who  is 
ignorant  enough  to  apply  any  paint  material  in  a  closed 
room  does  not  deserve  to  be  a  painter.  Even  materials 
like  pure  spirits  of  turpentine,  which  are  known  to  have 
medicinal  qualities,  when  breathed  in  large  quantities  are 
supposed  to  produce  headache  and  vertigo,  and  the  fumes 
of  benzol,  benzine  and  alcohol  give  the  same  results; 
therefore  all  people  who  apply  paint  should  do  so  in  well- 
ventilated  rooms.  Large  vats  which  are  varnished  on  the 
interior  like  brewers'  vats,  or  water  tanks  which  are 
painted  on  the  inside,  are  generally  ventilated  by  the 
engineers  in  charge  by  having  fresh  air  pumped  in  con- 
tinually to  the  men  from  the  top  and  by  simply  pumping 
out  the  vapors  from  below,  as  practically  all  of  the 
materials  used  in  the  manufacture  of  paint  give  off  vapors 
which  are  heavier  than  air. 

Paint  vapors  are  also  inflammable,  and  any  fire 
resulting  from  careless  smoking  or  throwing  lighted 
matches  near  paint  is  likely  to  produce  disastrous  results, 
but  much  information  has  been  disseminated  on  this 
subject,  particularly  through  the  railroads,  who  now 
demand  caution  labels  printed  on  each  package  before 
it  is  shipped  with  the  result  that  many  lawsuits  which 
were  instituted  formerly  against  the  manufacturer  are 
not  permitted  today.  The  same  is  true  with  regard 
to  the  vapors  arising  from  paint.  It  has  been  a  practice 
among  certain  questionable  lawyers  to  institute  suits 
against  paint  manufacturers  for  illness,  headaches,  nausea, 
vertigo  and  such  other  physical  ills  as  have  resulted  from 
the  fumes  of  paint,  and  few  of  these  lawsuits  have  ever 
been  tried,  because  the  paint  manufacturer  in  former 
times  has  been  inclined  to  settle  a  suit  of  this  kind 
rather  than  go  to  court,  but  these  cases  are  not  as 
frequent  as  they  formerly  were  on  account  of  the  wide- 


PAINTERS'  HYGIENE  283 

spread  knowledge  of  the  subject.  Fumes  arising  from 
paint  are  not  dangerous  in  the  open  air,  but  if  a  painter 
is  careless  in  a  closed  room  it  is  certainly  his  fault,  and  a 
man  who  knows  so  little  about  paint  should  not  be  per- 
mitted to  use  it. 


CHAPTER  XXVIII 


THE  GROWTH  or  FUNGI  ON  PAINT 

FUNGI  must  not  be  confounded  with  bacteria.  Bac- 
teria are  invisible  micro-organisms,  and  whether  they 
thrive  on  paints  has  never  yet  been  established.  Their 
existence  in  oil  or  paint  media  has  never  been  proved. 

Experiments  made  by  the 
author  in  which  various 
bacteria  were  grown  in 
gelatin  or  agar  agar  have 
demonstrated  that  when 
turpentine,  benzine,  linseed 
oil,  varnish  or  paints  of 
any  character,  excepting 
those  containing  water,  were 
added,  they  rapidly  per- 
ished. Fungi,  however,  are 
No.  71.  OLIVE  GREEN  FUNGUS,  growing  totally  different  organisms. 

on    paint -Photomicrograph     X6oo.    A  fungus   is    derived    from  a 
PENICILIUM  CRUSTACEUM. 

spore    which    floats    in    the 

air  and  which  practically  is  a  microscopic  seed.  When 
this  falls  on  fertile  ground  it  sprouts  and  becomes  a  white 
downy  mass,  which  is  known  as  the  hypha.  This 
downy  mass  later  on  assumes  a  color,  which  may  be 
either  gray,  green,  yellow  or  black,  and  is  known  under 
the  popular  title  of  mildew,  which  is  in  reality  a  fungus 
or  micro-organic  growth  of  the  vegetable  type. 

What  may  be  poisonous  to  a  human  being  is  evi- 
dently non-poisonous  or  neutral  to  a  fungus,  for  fungi 

284 


THE  GROWTH  OF  FUNGI  ON  PAINT 


285 


can  grow  and  do  grow  on  practically  all  of  the  barium 
precipitates,  which  are  known  to  be  highly  poisonous. 

A  fungus  needs  both  warmth  and  moisture  for  its 
propagation,  and  so  we  will  frequently  find  that  on  the 
south  side  of  a  house  at  the  seashore,  where  moisture  will 
collect  and  the  temperature  will  be  fairly  uniform,  fungi 
will  sprout  on  a  painted  surface  and  frequently  destroy 
the  paint.  This  is  more  noticeable  in  the  tropics  than  it 


L 


No.  72.  PENICILIUM  CRUSTACEUM  — 
Photomicrograph  x6oo,  a  common 
green  or  cellar  fungus  which  grows  on 
many  forms  of  paint. 


NO.    73.    ASPERGILLTJS  NlGER 

—  Photomicrograph    xioo, 
old  fungus  found  on  paint. 


is  in  the  North,  and  more  noticeable  in  the  European 
countries  than  it  is  in  America,  for  the  humidity  in  the 
United  States  is  way  below  normal  for  more  than  half 
of  the  year  whereas  the  humidity  is  fairly  constant  in 
Europe  and  in  the  tropics.  Some  of  these  fungi  are  very 
disagreeable,  particularly  the  black  types,  which  will 
grow  on  the  interior  of  houses,  and  which  always  propa- 
gate better  in  a  cellar  than  they  do  in  a  garret,  for  light 
has  a  tendency  to  kill  them. 

The  fungi  that  are  found  on  paint  may  be  classified 
into  the  following  varieties: 


286 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


1.  Penicilium  Crustaceum  types,  of  which  there  are 
many  varieties,  but  all  of  which  are  greenish  or  olive 
grayish. 

2.  Aspergillus     Niger, 
which    is    distinctly    black 
and  very  tenacious. 

3.  Rhizopus   Nigricans, 
which  is  brown  and  black, 
and  which   appears   gener- 
ally in  the  Fall  of  the  year. 

4.  Aspergillus    Flavus, 
which  is  yellow  and  orange, 

and  which  grows  freely  on  No    74   ASPERGILLUS  NlGER_Photo_ 

a    putrid     Soil     Or    near    de-        micrograph    xioo,    black    fungus    fre- 

caying  vegetable  matter.          quently  found  on  paint  in  cellars- 
It    must    be    generally    understood    that    the    use    of 

fungicides    is    not    always    to    be    recommended,    for    in 

breweries,  malt  houses, 
rooms  which  have  swim- 
ming pools,  and  cellars 
which  have  been  used  for 
storage,  these  fungi  grow 
at  times,  and  it  seems  as 
if  there  is  nothing  which 

s\  BB    kills  them.      The  best  way 

£  to  get    rid    of   them    is    to 

wash  the  surface  copiously 
with  soap  and  water  and 
then  spray  a  mixture  of  car- 


No.  75.  ASPERGILLUS  FLAVUS — Photo- 
micrograph x6oo,  yellow  fungus  fre-  bolic  acid  and  formaldehyde 

quently     found     in    breweries    and    an(J    afterward    bichloride   of 

dairies,  thriving  on  paint. 

mercury,  but  a  man  apply- 
ing a  material  of  this  kind  must  use  a  mask  and  a 
respirator. 


THE   GROWTH   OF  FUNGI   ON   PAINT 


287 


Many  a  complaint  has  reached  a  paint  manufacturer 
that  his  paint  has  turned  black  in  spots  under  the  eaves 
of  a  roof  or  in  a  ground- 
floor  room,  and  the  manu- 
facturer on  account  of 
ignorance  has  supplied 
fresh  paint  free  of  charge, 
or  the  painter  has  done 
the  work  over  again,  when 
as  a  matter  of  fact  the 
fault  was  due  entirely  to 
fungus  growth.  It  is  well, 
therefore,  for  the  paint 

chemist  to  familiarize  him-  No.  76.  CLADOSPORIUM  HERBARUM  — 
Self  with  at  least  these  Photomicrograph  x6oo,  a  pale  fungus 
f  f  , ,  growing  on  damp  walls. 

few  fungi,  as  they  are  the 

principal  types  which  flourish  on  paint. 


ANALYSIS   OF  PAINT  MATERIALS 
ANALYSIS  OF  WHITE  LEAD 

Gravimetric  Methods  —  Estimation  as  PbSC>4 

Lead.  —  Dissolve  i  g.  in  dilute  acetic  acid,  filter,  wash 
and  weigh  the  insoluble  residue.  To  the  filtrate  add  10 
c.c.  of  dilute  sulphuric  acid-(m)  and  evaporate  on  the 
steam  bath.  Allow  to  cool,  dilute  cautiously  to  100  c.c., 
add  10  c.c.  of  alcohol  and  stir  well.  Filter  on  a  Gooch  or 
alundum  crucible,  wash  with  water  containing  i  per  cent 
of  sulphuric  acid  and  10  per  cent  of  alcohol,  and  finally 
with  alcohol  alone.  Dry  at  110°  C. 

Lead  sulphate  is  appreciably  soluble  in  concentrated 
sulphuric  acid  and  slightly  soluble  in  water.  It  is  practi- 
cally insoluble,  however,  in  i  per  cent  sulphuric  acid  and 
in  alcohol.  It  is  very  soluble  in  hot,  concentrated  am- 
monium acetate  solution. 

Estimation  as  PbCrCX 

Treat  i  g.  in  a  beaker  with  hot  water  and  just  suf- 
ficient acetic  acid  to  dissolve  the  white  lead,  using  no 
more  than  5  c.c.  of  acetic  acid  in  excess.  Filter  off  from 
the  insoluble  residue.  Dilute  to  100  c.c.,  heat  to  boiling 
and  add  an  excess  of  a  neutral,  saturated  solution  of 
potassium  dichromate  solution.  Allow  to  cool.  Filter 
on  a  Gooch  or  alundum  crucible,  wash  and  dry  at  130°  C. 

Volumetric  Methods  —  Estimation  as  Molybdate 

Dissolve  0.5  g.  of  white  lead  in  5  c.c.  of  concentrated 
hydrochloric  acid  by  boiling.  Add  25  c.c.  of  cold  water 

288 


ANALYSIS  OF  PAINT  MATERIALS  289 

and  proceed  as  indicated  below,  under  "Standardization 
of  Ammonium  Molybdate." 

Lead  is  precipitated  as  PbMo04  by  a  standard  solu- 
tion of  ammonium  molybdate  from  hot  solutions  slightly 
acid  with  acetic  acid.  The  solutions  required  are: 

(a)  Ammonium  molybdate  —  Dissolve  4.25  g.  in  i  litre  of  water 

(b)  Tannic  acid  solution  —  Dissolve  o.i  g.  in  20  c.c.  of  water 

Standardization  of  Ammonium  Molybdate.  —  Weigh  off 
about  0.2  g.  pure  lead  foil  in  a  small  Erlenmeyer  flask 
and  dissolve  in  6  c.c.  of  nitric  acid  (1:2).  Evaporate 
the  solution  just  to  dryness.  Treat  the  residue  with 
30  c.c.  of  water  and  5  c.c.  of  concentrated  sulphuric  acid 
and  shake  well.  The  precipitated  lead  sulphate  is  allowed 
to  settle,  filtered  and  washed  with  dilute  sulphuric  acid 
(1:10).  Filter  and  precipitate  are  placed  in  an  Erlen- 
meyer flask  and  boiled  with  10  c.c.  of  concentrated 
hydrochloric  acid  until  completely  disintegrated.  Then 
add  15  c.c.  more  of  concentrated  hydrochloric  acid,  25  c.c. 
of  cold  water  and  neutralize  with  ammonia  until  slightly 
alkaline  to  litmus  paper.  Reacidify  with  acetic  acid. 
Dilute  to  200  c.c.  with  hot  water  and  heat  to  boiling. 
Titrate,  using  the  tannic  acid  solution  as  outside  indicator, 
until  a  brown  or  yellow  coloration  is  obtained  with  the 
latter. 

Precautions.  —  Titration  must  be  carried  out  hot,  at 
about  90°  C.  If  the  solution  should  cool  down  in  the 
course  of  titration,  reheat  it.  Here,  as  in  the  case  of  the 
titration  of  zinc  with  potassium  ferrocyanide,  the  scheme 
of  dividing  the  solution  into  two  unequal  parts  may  be 
used. 

To  determine  the  excess  of  ammonium  molybdate 
necessary  to  affect  the  indicator,  place  in  an  Erlenmeyer 
flask  25  c.c.  of  hydrochloric  acid,  neutralize  until  slightly 
alkaline  to  litmus,  then  reacidify  with  acetic  acid.  Dilute 


290  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

to  200  c.c.,  heat  to  boiling,  and  add  ammonium  molybdate 
drop  by  drop  until  the  outside  indicator  is  affected. 

Antimony  and  bismuth  do  not  affect  the  results 
obtained  by  this  method.  Barium  and  strontium  give 
very  low  results,  while  calcium  yields  but  slightly  low 
results.  The  alkaline  earth  sulphates  tend  to  retard  the 
solution  of  the  lead.  This  difficulty  can  be  overcome  by 
thoroughly  washing  the  lead  sulphate  and  then  boiling  it 
with  sufficient  ammonium  acetate. 

Carbon  Dioxid  and  Combined  Water.  —  i  g.  of  white 
lead  is  weighed  off  in  a  porcelain  boat.  The  latter  is 
then  placed  in  a  combustion  tube  and  heated  in  a  current 
of  dry  air  free  from  carbon  dioxid.  The  water  is  col- 
lected in  calcium  chloride  tubes,  and  the  carbon  dioxid 
in  potash  bulbs  or  soda  lime  tubes. 

Carbon  dioxid  may  be  determined  by  evolution  by 
treating  white  lead  with  dilute  nitric  acid.  Use  a  reflux 
condenser  in  connection  with  the  evolution  flask  and  dry 
the  carbon  dioxid  by  passing  through  calcium  chloride 
before  absorbing  in  the  potash  bulbs  or  soda  lime  tubes. 

BASIC  LEAD  SULPHATE 

Lead  and  Zinc  (gravimetric}.  —  Digest  i  g.  for  ten  min- 
utes in  the  cold  with  20  c.c.  of  10  per  cent  sulphuric  acid. 
Filter,  keeping  most  of  the  residue  in  the  beaker,  and 
wash  twice  by  decantation  with  i  per  cent  sulphuric  acid. 
The  nitrate  from  the  sulphuric  acid  teatment  is  re- 
served for  the  determination  of  zinc  which  is  carried  out 
by  any  of  the  methods  outlined  under  "Zinc  Oxid." 
Preferably  precipitate  as  phosphate.  Calculate  the  zinc 
to  ZnO. 

Dissolve  the  residue  in  the  beaker  with  hot  concen- 
trated slightly  acid  ammonium  acetate  solution  pouring  the 
solution  through  the  filter.  Wash  the  latter  with  ammo- 


ANALYSIS  OF  PAINT  MATERIALS  291 

nium  acetate  and  then  with  hot  water.  Dilute  to  200  c.c., 
add  an  excess  of  a  neutral  saturated  solution  of  potassium 
dichromate  and  bring  to  boiling.  Allow  to  cool,  and  filter 
on  a  Gooch  or  alundum  crucible.  Dry  at  130°  and  weigh 
as  PbCrO4. 

Lead  (volumetric).  --Treat  0.5  g.  sample  with  30  c.c.  of 
water  and  5  c.c.  of  concentrated  sulphuric  acid,  and 
proceed  as  outlined  under  "Estimation  as  Molybdate." 

Sulphates.1  --  Dissolve  0.5  g.  by  boiling  in  a  mixture  of 
25  c.c.  water,  10  c.c.  aqua  ammonia  and  enough  con- 
centrated hydrochloric  acid  to  give  a  slight  excess.  Dilute 
to  200  c.c.  and  add  a  piece  of  pure  thick  aluminium  foil 
large  enough  to  nearly  cover  the  bottom  of  the  beaker. 
This  should  be  kept  at  the  bottom  by  means  of  a  glass 
rod.  Boil  gently  until  the  lead  is  precipitated.  When 
the  lead  no  longer  adheres  to  the  aluminium,  the  precipi- 
tation may  be  considered  complete.  Filter  and  wash 
with  hot  water.  A  little  sulphur-free  bromine  water  is 
added  to  the  filtrate,  the  latter  is  boiled,  and  sulphates 
determined  by  precipitation  with  barium  chloride  in 
the  ordinary  way. 

If  desired  the  sulphates  may  be  determined  as  indicated 
under  Analysis  of  "Zinc  Lead." 

Sulphur  Dioxid.  —  Digest  about  2  g.  in  the  cold  with 
5  per  cent  sulphuric  acid,  and  titrate  with  —  iodine  solu- 
tion, using  starch  as  indicator. 

ANALYSIS  or  ZINC  LEAD 

Lead.  —  i  g.  of  the  material  is  heated  on  the  steam 
bath  with  20  c.c.  of  hydrochloric  acid  (1:1)  and  5  g. 
of  ammonium  chloride.  The  solution  is  diluted  to  250 
c.c.  with  hot  water  and  boiled.  This  treatment  should 
suffice  to  dissolve  a  pure  zinc  lead. 

1  Holley,  "Analysis  of  Paint  and  Varnish  Products,"  1912,  p.  104. 


292  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

The  insoluble  residue,  if  any,  is  filtered,  weighed,  and 
examined  for  impurities.  Neutralize  the  filtrate  with 
ammonia,  reacidify  slightly  with  hydrochloric  acid,  and 
precipitate  the  lead  with  hydrogen  sulphide. 

Allow  the  precipitate  to  settle,  filter  off  the  liquid, 
and  wash  the  precipitate  several  times  by  decantation 
with  hydrogen  sulphide  water.  The  precipitate  is  finally 
dissolved  in  hot,  dilute  nitric  acid,  treated  with  an  excess 
of  sulphuric  acid,  and  evaporated  to  S03  fumes. 

Allow  to  cool,  dilute  cautiously  with  100  c.c.  of  cold 
water,  filter  off  the  precipitated  lead  sulphate  on  a  Gooch 
crucible,  wash  several  times  with  dilute  sulphuric  acid, 
and  finally  once  with  alcohol.  Dry  at  130°  C.,  and 
weigh  as  PbS04. 

Zinc.  —  The  filtrate  from  the  lead  sulphide  precipitate 
is  boiled  to  expel  hydrogen  sulphide,  treated  while  hot 
with  a  few  drops  of  HNO3,  then  rendered  slightly  am- 
moniacal,  and  any  precipitate  which  is  formed  is  filtered 
off.  The  filtrate  is  then  slightly  acidified  with  acetic 
acid,  heated  to  boiling  and  a  stream  of  sulphuretted 
hydrogen  passed  in  to  precipitate  the  zinc.  The  latter 
is  filtered  and  washed  with  water  containing  a  small 
amount  of  acetic  acid  saturated  with  hydrogen  sulphide, 
using  a  Gooch  or  alundum  crucible  for  filtering. 

In  filtering  zinc  sulphide,  keep  the  crucible  full  of 
liquid  or  wash  water  until  the  precipitate  is  completely 
washed.  Only  then  may  the  precipitate  be  allowed  to 
drain  free  from  wash  water. 

The  zinc  sulphide  is  then  dissolved  in  dilute  hydro- 
chloric acid,  the  sulphuretted  hydrogen  expelled  by  boiling, 
and  the  zinc  determined  either  volumetrically  by  the 
ferro-cyanide  method  or  gravimetrically  by  precipitation 
with  a  slight  excess  of  sodium  carbonate,  and  ignition  to 
oxid. 


ANALYSIS  OF  PAINT  MATERIALS  293 

Calcium  and  Magnesium.  -  -  The  filtrate  from  the  zinc 
sulphide  is  evaporated  to  a  small  bulk  and  the  calcium 
determined  by  precipitating  hot  from  a  slightly  ammoni- 
acal  solution  with  ammonium  oxalate.  Magnesium  is 
determined  as  usual. 

Soluble  Salts.  —  To  determine  the  presence  of  zinc  sul- 
phate, i  g.  is  digested  with  100  c.c.  of  water,  filtered, 
and  the  sulphate  determined  in  the  filtrate  as  usual,  with 
barium  chloride. 

Total  Sulphates.  —  Dissolve  i\  g.  of  sodium  car- 
bonate in  a  beaker  with  25  c.c.  of  water,  add  0.5  g. 
of  the  sample,  boil  gently  for  about  ten  minutes  and 
allow  to  stand  for  several  hours.  Dilute  with  hot  water, 
filter  and  wash  until  the  filtrate  is  about  200  c.c. 

Render  the  filtrate  slightly  acid  with  hydrochloric, 
boil  to  expel  carbon  dioxid  and  precipitate  the  sulphate 
with  a  slight  excess  of  barium  chloride  solution. 

Filter,  wash  and  weigh  as  BaSO4.  Calculate  the  lat- 
ter to  PbSO4. 

ZINC  OXID 

Insoluble.  —  Dissolve  i  g.  in  hot  dilute  acetic~licid. 
Filter,  wash  and  weigh  any  insoluble  residue.  If  the 
latter  is  very  small  in  quantity,  it  should  be  deter- 
mined by  dissolving  a  proportionately  larger  quantity  of 
zinc  oxid. 

Zinc.  —  Neutralize  the  filtrate  with  ammonia,  then 
make  faintly  acid  with  acetic  acid,  dilute  to  300  c.c.,  and 
precipitate  with  sulphuretted  hydrogen.  The  solution 
should  be  kept  hot  during  the  precipitation,  and  should 
smell  strongly  of  hydrogen  sulphide  at  the  end.  Allow 
the  precipitate  to  settle,  decant  through  an  alundum  or 
Gooch  crucible,  keeping  the  crucible  full  of  liquid  during 
the  filtration,  wash  the  precipitate  in  the  beaker  with  a 


294  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

hot  2  per  cent  acetic  acid  solution  saturated  with  hydro- 
gen sulphide,  finally  transferring  the  zinc  sulphide  to  the 
crucible  and  allowing  the  last  wash  water  to  drain  com- 
pletely. The  zinc  sulphide  is  dissolved  in  dilute  hydro- 
chloric acid  and  boiled  to  expel  H2S  (test  with  lead  acetate 
paper  held  in  the  escaping  vapors  from  the  beaker  or 
flask  to  show  the  presence  of  hydrogen  sulphide). 

Gravimetric  Methods  for  Zinc.  —  (a)  Precipitation  as  Phosphate 

The  solution  is  rendered  very  faintly  acid  by  almost 
completely  neutralizing  with  ammonia,  diluted  to  150  c.c. 
and  heated  on  the  steam  bath.  Add  to  the  solution  on 
the  steam  bath  about  ten  times  as  much  di-ammo- 
nium  phosphate  1  as  zinc  present.  Heat  for  1 5  minutes 
longer.  The  crystalline  zinc  ammonium  phosphate  is 
filtered  through  a  Gooch  or  alundum  crucible,  washed 
with  hot  i  per  cent  ammonium  phosphate  solution  until 
free  from  chlorides,  then  with  cold  water  and  finally  with 
50  per  cent  alcohol.  Dry  at  120°  C.  for  one  hour  and 
weigh  as  ZnNH4PO4. 

(6)  Precipitation  as  Carbonate 

The  zinc  chloride  solution  is  carefully  neutralized  in 
the  cold  with  sodium  carbonate  solution  until  a  precipi- 
tate begins  to  form.  The  solution  is  then  heated  to 
boiling,  and  precipitation  completed  by  adding  a  slight 
excess  of  sodium  carbonate  (use  phenolphthalein  as  indi- 
cator). Ammonium  salts  must  not  be  present.  Filter  on 
a  Gooch  crucible,  wash,  ignite  and  weigh  as  ZnO. 

Volumetric  Method.  —  Zinc  is  precipitated  from  hot 
somewhat  acid  solutions  by  the  addition  of  potassium 
ferro-cyanide  according  to  the  following  reaction: 

1  Dissolve  in  cold  water  and  add  dilute  ammonia  until  faintly 
pink  with  phenolphthalein. 


ANALYSIS  OF  PAINT  MATERIALS  295 


3ZnCl2  +  2K4FeC6N6  =  Zn3K2Fe2(CN)i2  +  6KC1 

The  end  point  is  indicated  by  a  solution  of  uranium  ni- 
trate as  outside  indicator.  A  brown  coloration  is  produced 
when  a  drop  of  the  solution  containing  the  excess  of 
potassium  ferrocyanide  is  added  to  a  drop  of  uranium 
nitrate  solution  on  a  spotting  tile. 

Solutions  Potassium  Ferrocyanide.  —  Dissolve  21.6  g. 
of  crystallized  salt,  K4FeC6N6-3H2O  in  cold  water  and 
dilute  to  one  liter.  One  c.c.  of  this  solution  is  equivalent 
to  about  0.005  g-  zmc- 

Uranium  nitrate  ...............  5%  solution 

Ammonium  chloride  ...........  10  g.  per  liter 

Standardization  of  Ferrocyanide.  —  Weigh  out  two  or 
three  portions  of  0.2  to  0.25  g.  of  pure  ignited  zinc  oxid. 
Dissolve  in  10  c.c.  of  hydrochloric  acid  (1:2),  add  sodium 
carbonate  solution  or  ammonia  until  a  slight  permanent 
precipitate  is  formed,  redissolve  the  latter  with  one 
or  two  drops  of  hydrochloric  acid,  add  6  c.c.  of  concen- 
trated hydrochloric  acid  and  10  g.  of  ammonium  chloride. 
Dilute  to  1  80  c.c.,  heat  to  70°  C.  and  titrate  with  ferro- 
cyanide solution  until  the  end  point  is  reached.  To 
determine  the  end  point  rapidly  divide  the  zinc  solution 
into  two  unequal  parts.  Titrate  the  smaller  part  run- 
ning in  the  ferrocyanide  solution  i  c.c.  at  a  time.  When 
an  excess  has  been  added  pour  in  the  rest  of  the  zinc  so- 
lution, run  in  i  c.c.  less  than  the  quantity  of  potassium 
ferrocyanide  previously  added,  and  finish  the  titration 
drop  by  drop. 

A  blank  must  be  deducted  because  of  the  excess  of 
potassium  ferrocyanide  required  to  develop  the  brown 
coloration  with  uranium  solution. 

To  determine  the  allowance,  add  6  c.c.  of  concentrated 
hydrochloric  acid  and  10  g.  of  ammonium  chloride  to  200 


296  CHEMISTRY  AND    TECHNOLOGY  OF  PAINTS 

c.c.  of  water  in  a  beaker,  heat  to  70°  C.,  and  add  the 
ferrocyanide  solution  until  the  brown  coloration  is  ob- 
tained with  the  outside  indicator.  The  correction  should 
be  less  than  0.5  c.c.  Deduct  this  amount  from  all  future 
titrations. 

Determination  of  Zinc.  -  -  To  determine  zinc  in  the 
solution  obtained  by  dissolving  ZnS  in  hydrochloric  acid 
and  expelling  hydrogen  sulphide,  neutralize  with  ammonia 
or  sodium  carbonate,  reacidify  slightly  with  dilute  hydro- 
chloric acid,  and  proceed  as  outlined  under  "Standardiza- 
tion of  Ferrocyanide."  The  presence  of  a  small  amount 
of  lead  does  not  interfere  with  the  accuracy  of  the  above 
method. 

Soluble  Impurities.  —  Most  zinc  oxids  are  contami- 
nated with  small  quantities  of  cadmium  and  traces  of  iron, 
copper  and  lead.  The  cadmium  l  is  best  determined  by 
dissolving  a  relatively  large  amount,  25  to  50  g.,  of  zinc 
oxid  in  dilute  sulphuric  acid,  filtering,  diluting  to  400  c.c. 
and  precipitating  as  sulphide  in  the  presence  of  an 
excess  of  about  5  c.c.  of  concentrated  sulphuric  acid  in  100 
c.c.  of  solution.  Filter,  wash,  redissolve  in  sulphuric  acid 
and  reprecipitate  as  sulphide.  Dissolve  into  a  crucible 
with  as  small  an  amount  of  sulphuric  acid  as  possible. 
Evaporate  cautiously  and  ignite  to  CdSO4. 

LITHOPONE 
METHOD    I 

Zinc  Oxid.  —  Digest  i  g.  with  100  c.c.  of  i  per  cent 
acetic  acid  at  room  temperature  for  one  half  hour. 
Filter,  wash  and  weigh  the  insoluble.  The  loss  in 
weight  represents  the  zinc  oxid  present. 

1  For  electrolytic  method  of  determining  Cadmium,  see  E.  F. 
Smith's  "  Electro-Analysis." 


ANALYSIS  OF  PAINT  MATERIALS  297 

Insoluble  and  Total  Zinc. --Treat  i  g.  in  a  200  c.c. 
beaker  with  10  c.c.  of  concentrated  hydrochloric  acid, 
mix,  and  add  in  small  portions  i  g.  of  potassium  chlorate 
(this  should  be  carried  out  under  a  hood);  evaporate  on 
the  steam  bath  to  ^  the  volume.  Dilute  with  hot  water, 
add  5  c.c.  of  dilute  sulphuric  acid  (1:10),  boil,  filter,  and 
weigh  the  insoluble.  The  latter  is  barium  sulphate.  The 
zinc  is  determined  in  the  filtrate  by  the  methods  outlined 
under  "Zinc  Oxid." 

METHOD    II 

Soluble  Salts.  -  -  Treat  2  g.  of  lithopone  with  100 
c.c.  of  hot  water.  Digest  for  a  few  minutes  and  filter 
on  a  Gooch  crucible  (test  the  filtrate  for  Ba,  Zn  and  SO4). 
Wash  with  hot  water  and  finally  once  with  alcohol. 
Dry  the  crucible  in  the  air  oven  at  100°  C.  and  deter- 
mine loss  in  weight.  The  latter  is  equal  to  the  per- 
centage of  moisture  present  plus  the  water  soluble 
salts. 

Zinc  Oxid.  —  Digest  for  J  hour,  without  warming,  a  i 
g.  sample  with  100  c.c.  of  i  per  cent  acetic  acid.  Filter, 
wash,  and  determine  the  zinc  in  the  filtrate  gravimetrically 
or  volumetricalty,  as  outlined  under  "Zinc  Oxid."  Cal- 
culate to  ZnO. 

Zinc  Sulphide. — Transfer  the  filter  paper  and  residue 
to  a  beaker,  treat  with  dilute  hydrochloric  acid  (1:4)  and 
boil  to  drive  off  H2S.  Filter,  wash  with  hot  water,  and 
determine  the  zinc  in  the  filtrate  by  the  usual  methods. 
Report  as  ZnS. 

Barium  Sulphate.  -  -  The  residue  is  dried,  ignited, 
treated  with  a  few  drops  of  concentrated  sulphuric  acid 
in  the  crucible,  again  ignited  and  weighed  as  BaS04. 
Test  the  latter  for  clay  or  silica.  Should  any  be  present, 
treat  the  residue  with  hydrofluoric  and  sulphuric  acids 


298  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

in  a  platinum  crucible  and  evaporate  to  dryness.     The 
loss  in  weight  represents  silica. 


RED  LEAD  AND  ORANGE  MINERAL 

Lead  Peroxid  (Method  7).  — Dissolve  0.5  g.  in  a  beaker 
with  30  c.c.  of  2N  nitric  acid,  heat  to  boiling  to  complete 
solution.  Add  25  c.c.  N/5  oxalic  acid,  accurately  meas- 
ured from  a  pipette  or  burette,  boil  and  titrate  hot 
'with  KMnO4. 

A  blank  containing  the  same  quantities  of  nitric  acid 
and  oxalic  acid  is  also  titrated  against  the  permanganate. 
The  difference  between  the  two  titrations  represents  the 
amount  of  Pb02  reduced  by  oxalic  acid. 

Pb3O4+  4HN03  =  2Pb  (NO3)2+  H20  +  H3PbO3 
Pb02  +  H2C204  =  PbO  +  H2O+  2C02 

Lead  Peroxid  (Method  II).  —  Mix  together  in  a  small 
beaker  1.2  g.  of  potassium  iodide,  15  g.  sodium  acetate 
and  5  c.c.  of  50  per  cent  acetic  acid.  Weigh  off  0.5  g.  of 
red  lead  in  a  150  c.c.  Erlenmeyer  flask  and  add  the  above 
mixture  to  it.  Stir  until  the  lead  is  completely  dis- 
solved. Dilute  to  25  c.c.,  and  titrate  with  N/io  sodium 
thiosulphate,  using  starch  as  indicator. 

A  little  red  lead,  especially  when  it  is  not  very  fine  in 
texture,  at  first  resists  solution  in  the  potassium  iodide 
mixture,  but  dissolves,  on  mixing,  toward  the  end  of  the 
titration.  Proceed  with  the  titration  as  soon  as  the  lead  is 
in  solution,  so  as  to  avoid  loss  of  iodine  by  volatilization. 

The  reaction  involved  in  the  above  method  is 

Pb02  +  4HI  =  PbI2  +  2H2O  +  I2 

The  lead  peroxid  is  reduced  in  the  presence  of  an 
excess  of  sodium  acetate  when  treated  with  potassium 
iodide  in  acetic  acid  solution. 


ANALYSIS  OF  PAINT  MATERIALS  299 


ANALYSIS  OF  IRON  Oxros 

Moisture.  —  Heat  2  g.  in  the  air  oven  at  105°  C.  for 
two  hours. 

Loss  on  Ignition.  —  Ignite  i  g.  in  a  porcelain  crucible 
to  a  red  heat.  The  loss  in  weight  consists  of  hygros- 
copic moisture,  water  of  combination,  sometimes  organic 
matter,  and  carbon  dioxid  due  to  the  presence  of  car- 
bonates. 

Insoluble.  —  Digest  i  g.  of  the  oxid  with  20  c.c.  of 
hydrochloric  acid  (1:1)  on  the  hot  plate  for  15  minutes. 
Filter,  wash  and  weigh  the  insoluble  residue.  The 
latter  may  be  examined  to  determine  the  presence  of 
barytes,  clay  or  silica. 

Iron  Oxid.  —  Weigh  off  from  0.3  to  i.o  g.,  depend- 
ing upon  the  amount  of  iron  oxid  present,  treat  with 
20  c.c.  of  hydrochloric  acid  (i :  i)  on  the  hot  plate  until 
the  residue  is  white,  and  while  hot  reduce  with  a  strongly 
acid  stannous  chloride  solution  until  the  iron  solution 
is  colorless,  using  only  one  or  two  drops  in  excess.  Wash 
down  the  sides  of  the  beaker  and  the  cover  glass  with  a 
little  water,  add  all  at  once  10  c.c.  of  a  saturated  solution 
of  mercury  bichloride,  stir,  and  wash  the  whole  into  a 
large  beaker  containing  400  c.c.  of  cold  distilled  water  to 
which  has  been  added  10  c.c.  of  preventive  solution. 
Titrate  writh  N/io  potassium  permanganate  to  a  faint 
pink. 

In  the  case  of  magnetic  oxids  and  certain  purple 
oxids,  solution  is  facilitated  by  the  addition  of  i  to  3  c.c. 
of  a  25  per  cent  stannous  chloride  solution.  Should  the 
residue  after  digestion  on  the  hot  plate  still  show  greenish 
or  black,  filter,  wash,  and  determine  the  iron  in  the  soluble 
portion  as  outlined  below. 


300  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

To  determine  iron  in  the  insoluble  portion,  fuse  in  a 
porcelain  crucible  with  five  times  its  weight  of  potassium 
bisulphate  for  about  J  hour.  Cool,  dissolve  in  water  and 
filter.  Determine  iron  in  the  filtrate  after  reduction  as 
outlined  below. 

Stannous  Chloride  Solution.  —  Dissolve  50  g.  of  stan- 
nous  chloride  in  100  c.c.  of  hydrochloric  acid  and  dilute 
to  1000  c.c.  To  preserve  the  solution,  always  keep  a 
few  pieces  of  metallic  tin  at  the  bottom  of  the  bottle. 

PREVENTIVE  SOLUTION: 

Crystallized  Manganese  Sulphate 67  g. 

Water 500  c.c. 

Syrupy  Phosphoric  Acid  (Sp.  Gr.  1.7).  .  .138  c.c. 
Concentrated  Sulphuric  Acid 130  c.c. 

Dissolve  in  the  order  named  and  dilute  to  i  liter. 

ANALYSIS  OF  UMBERS  AND  SIENNAS 

To  0.5  to  i.o  g.,  depending  upon  the  amount  of  iron 
oxid  present,  in  a  casserole,  add  20  c.c.  of  hydrochloric 
acid  (1:1)  and  0.35  g.  potassium  chloride  (or  0.25  g. 
ammonium  chloride),  and  evaporate  to  dryness  on  the 
steam  bath.  Heat  for  10  minutes  longer  to  expel  hydro- 
chloric acid.  Dissolve  the  soluble  salts  in  about  25  c.c. 
of  hot  water,  filter  and  wash  the  insoluble  residue.  The 
latter  is  dried,  ignited  and  weighed,  and  reported  as 
insoluble  or  silicious  matter.  (When  necessary  analyze 
this  separately  as  indicated  under  "Analysis  of  Silica, 
Asbestine  or  Clay".) 

To  the  filtrate,  heated  almost  to  boiling,  there  is 
added  3.0  g.  of  sodium  acetate  for  every  0.3  g.-  of  iron 
in  solution,  and  400  c.c.  of  boiling  water.  Heat  to 
incipient  boiling.  By  this  means  the  iron  is  quantita- 
tively precipitated  as  a  basic  acetate,  while  manganese 


ANALYSIS  OF  PAINT  MATERIALS  301 

and  other  divalent  metals  of  the  group  stay  in  solution. 
The  precipitate  is  allowed  to  settle,  the  solution  decanted 
off  and  filtered;  the  precipitate  is  washed  several  times 
with  hot  water,  dissolved  in  a  small  amount  of  hot  dilute 
hydrochloric  acid,  and  either  precipitated  with  ammonia 
or  determined  volumetrically  as  under  "Analysis  of  Iron 
Oxids."  The  nitrate  is  evaporated  to  about  half  its 
volume,  treated  with  an  excess  of  bromine  water,  and 
then  boiled  until  the  precipitated  manganese  dioxid  be- 
comes floccular.  The  precipitate  is  then  filtered  off, 
washed,  and  ignited  to  Mn304. 

Calcium  and  magnesium  are  determined  in  the  fil- 
trate in  the  usual  way.  When  appreciable  quantities  of 
these  two  elements  are  present,  it  is  best  to  separate  the 
manganese  by  precipitation  as  sulphide. 

To  determine  manganese  as  sulphide,  heat  the  neutral 
solution  to  boiling,  add  an  excess  of  ammonia  and  am- 
monium sulphide,  and  continue  the  boiling  until  the  man- 
ganese sulphide  becomes  a  dirty  green.  Decant  through 
a  Gooch  crucible,  using  gentle  suction,  keeping  the  cru- 
cible filled  all  the  tirne.  Wash  the  precipitate  twice  by 
decantation  with  5  per  cent  ammonium  nitrate  solution  con- 
taining a  little  ammonium  sulphide,  add  to  the  crucible 
and  filter,  allowing  the  crucible  to  drain.  The  filtrate 
is  acidified  with  dilute  acetic  acid  boiled  to  expel  hydro- 
gen sulphide,  and  the  calcium  and  magnesium  deter- 
mined as  usual.  The  precipitated  manganese  sulphide 
is  dissolved  in  a  little  hot  dilute  hydrochloric  acid, 
evaporated  to  expel  hydrogen  sulphide,  and  precipitated 
as  carbonate  or  phosphate.  In  the  first  case  the  man- 
ganese is  ignited  and  weighed  as  Mn3O4. 

Colorimetric  Determination  of  Manganese.1  —  Dissolve 

1  Treadwell,  Volume  II,  pages  127,  128.  Marshall,  Chem.  News, 
83,  76  (1904).  Walters,  Chem.  News  84/239  (1904). 


302  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

0.5  g.  of  umber  or  sienna  in  about  10  c.c.  of  hydrochloric 
acid  (1:1)  in  a  casserole,  add  an  excess  of  nitric  acid  and 
evaporate  to  dryness  to  drive  off  the  hydrochloric  acid. 
Cool,  add  20  c.c.  of  cold  nitric  acid  (specific  gravity  1.2) 
filter  and  wash  with  the  least  quantity  of  cold  water  into 
a  100  c.c.  graduated  flask.  Make  up  to  the  mark. 
Remove  10  c.c.  by  means  of  a  pipette  to  a  graduated 
test  tube,  add  10  c.c.  of  silver  nitrate  1  solution,  and  2.5 
c.c.  of  ammonium  persulphate 2  solution,  mix,  and  place  the 
tubes  in  water  at  80  to  90°  C.  until  bubbles  of  gas  arise, 
and  remain  at  the  top  for  a  few  seconds.  Cool  the  test 
tubes  and  compare  against  standard  tubes  made  with 
known  amounts  of  manganese. 

MERCURY  VERMILION 

This  pigment  is  very  expensive  and  therefore  quite 
often  adulterated.  The  possible  adulterants  are  organic 
lakes,  orange  lead  chromes,  red  lead,  and  iron  oxids,  as 
well  as  barytes,  silica  or  clay. 

Its  high  specific  gravity  (8.2)  and  its  insolubility  in 
alkalies,  and  in  any  one  acid,  distinguish  it  from  all  other 
pigments  of  like  color. 

A  pure  vermilion  can  be  volatilized  completely  on 
heating,  leaving  no  residue.  On  account  of  the  ex- 
tremely toxic  properties  of  mercury  vapors,  such  volatili- 
zation should  be  carried  out  in  a  hood  having  a  good 
draft. 

Barytes,  Silica  or  Clay.  —  Dissolve  2  g.  in  aqua  regia, 
or  hydrochloric  acid  with  a  little  potassium  chlorate,  and 
after  evaporating  to  dryness  take  up  with  boiling  water 
and  a  little  hydrochloric  acid.  Filter  and  weigh  the 
residue. 

1  1.38  g-AgnOs  in  1000  c.c.  of  water. 

2  20%  solution. 


ANALYSIS  OF  PAINT  MATERIALS  303 

Lead.  —  Evaporate  the  filtrate  from  the  above  with  an 
excess  of  dilute  sulphuric  acid  to  SO3  fumes,  and  deter- 
mine lead  as  PbSO4.  (Calcium  must  be  absent.) 

Free  mercury,  free  sulphur  and  iron  may  be  identified 
by  dissolving  the  mercury  vermilion  in  potassium  mono- 
sulphide  (1:1),  in  which  it  dissolves  readily.  The  solu- 
tion is  colorless  after  the  iron  sulphide  has  settled  out. 
Free  mercury  settles  to  the  bottom  of  the  dish  as  a  gray 
sediment. 

Free  sulphur  is  recognized  by  the  yellow  coloration  of 
the  solution.  It  may  also  be  detected  in  the  usual  way  by 
digesting  with  potassium  hydroxid  or  extraction  with 
carbon  disulphide  (if  present  in  crystalline  form).  The 
quantitative  determination  is  carried  out  by  extracting  with 
soda  solution  and  oxidation  to  sulphate. 

For  separating  foreign  adulterations  such  as  barytes, 
clay,  litharge,  chrome  red,  brick  dust,  etc.,  potassium  sul- 
phide may  be  used  to  advantage.  After  filtering,  wash 
with  dilute  KOH  solution  and  not  with  water,  otherwise 
the  Brunner's  salt  decomposes  with  separation  of  black  HgS. 

The  coal  tar  colors  are  identified  by  extraction  with 
alcohol;  carmines  by  the  drop  test  with  ammonia  on  filter 
paper. 

For  detecting  arsenic  sulphide,  boil  with  caustic  soda, 
acidify  with  hydrochloric  acid  and  introduce  H2S  gas  into 
the  solution. 

ANALYSIS  OF  CHROME  YELLOWS  AND  ORANGES 

Organic  Matter.  — Test  with  alcohol  to  determine  pres- 
ence of  organic  coloring  matter. 

Insoluble.  —  Boil  i  g.  for  about  5  minutes  with  20  c.c. 
of  concentrated  hydrochloric  acid,  adding  i  or  2  c.c.  of 
alcohol  drop  by  drop.  Dilute  with  about  100  c.c.  of 
boiling  water.  Boil  a  few  minutes  longer.  Filter,  wash 


304  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

with  boiling  water,  and  weigh  the  insoluble.  Test  the 
latter  for  barium  sulphate,  clay  or  silica. 

Lead.  -  -  Neutralize  the  nitrate  with  ammonia  until  a 
slight  permanent  precipitate  appears.  Reacidify  slightly, 
using  an  excess  of  not  more  than  1.5  c.c.  of  concentrated 
hydrochloric  acid  in  100  c.c.  of  solution.  Dilute  to  200 
c.c.  Precipitate  the  lead  with  hydrogen  sulphide.  Fil- 
ter, wash  with  H2S  water,  dissolve  the  PbS  in  hot  dilute 
nitric  acid,  boil  to  expel  H2S,  add  10  c.c.  of  dilute  H2SO4 
(1:1),  evaporate  to  fumes  of  S03  and  determine  lead 
gravimetrically  or  volumetrically  as  outlined  under 
"White  Lead." 

Chromium.  —  Evaporate  the  alcoholic  nitrate  from  the 
PbSO4  almost  to  dryness  and  mix  with  the  filtrate  from 
PbS.  The  chromium  is  determined  by  precipitating  hot 
with  a  slight  excess  of  ammonia.  Filter,  wash,  ignite  and 
weigh  as  Cr2O3. 

Zinc.  —  The  filtrate  from  chromium  hydroxid  is  ana- 
lyzed for  zinc  by  precipitating  with  hydrogen  sulphide. 
See  "Zinc  Oxid." 

CHROME  GREENS 

Preliminary  Test.  —  Determine  the  presence  of  organic 
coloring  matter  by  extraction  with  alcohol. 

Insoluble.  —  In  a  small  evaporating  dish  heat  i  g. 
sample  at  as  low  a  temperature  as  possible  until  the  blue 
color  is  completely  discharged.  Transfer  to  a  beaker,  and 
boil  with  20  c.c.  of  concentrated  hydrochloric  acid  and  a 
little  alcohol  to  dissolve  the  soluble  portion.  Dilute  with 
hot  water,  boil,  filter,  wash,  and  weigh  the  insoluble  por- 
tion. Examine  the  latter  for  silica,  clay  or  barytes. 

Lead.  —  Determine  in  the  filtrate  after  neutralizing 
with  ammonia  and  reacidifying  slightly  with  hydro- 
chloric acid  as  under  "Chrome  Yellows." 


ANALYSIS  OF  PAINT  MATERIALS  305 

Chromium,  Iron  and  Aluminium. — Boil  the  filtrate  from 
the  lead  sulphide  to  expel  hydrogen  sulphide,  add  a  few 
drops  of  nitric  acid  and  about  2  g.  of  ammonium  chloride. 
Heat  to  boiling,  and  precipitate  iron,  aluminium,  and 
chromium  as  hydroxids  with  ammonia  in  slight  excess. 
Filter  and  wash  the  precipitates.  Dissolve  the  mixed 
hydroxids  in  a  small  amount  of  hot  dilute  hydrochloric 
acid  and  dilute  to  150  c.c.  Heat  to  boiling  and  treat  with 
an  excess  of  sodium  hydroxid,  and  bromine  water. 
Filter  and  wash.  Redissolve  the  ferric  hydroxid  in 
dilute  hydrochloric  acid,  and  determine  iron  by  the  usual 
methods. 

The  filtrate  is  acidified  faintly  with  hydrochloric  acid 
and  aluminium  hydroxid  precipitated  with  a  slight  excess 
of  ammonia. 

The  filtrate  from  aluminium  hydroxid  is  carefully 
acidified  with  acetic  acid,  and  the  chromium  precipitated 
by  the  addition  of  barium  acetate  to  the  hot  solution. 
Allow  to  stand  for  some  time,  and  filter  through  a  Gooch 
or  alundum  crucible  (using  gentle  suction).  Wash  with 
alcohol,  and  dry  in  hot  closet.  Finally  ignite  at  a  dull 
red  heat  by  suspending  the  crucible  inside  a  larger  por- 
celain crucible  by  means  of  an  asbestos  ring.  If  desired 
the  chromium  present  as  alkali  chromate  may  be  reduced 
to  chromic  salt  by  evaporating  with  hydrochloric  acid 
and  alcohol.  The  chromium  may  then  be  precipitated 
by  ammonia  and  weighed  after  ignition  as  Cr2O3. 

Calcium  and  Magnesium.  —  Determine  as  usual  in  the 
filtrate  from  iron,  aluminium  and  chromium  hydroxids. 

Sulphates.  -  -  Treat  i  g.  as  mentioned  in  the  second 
paragraph  of  this  section.  Determine  sulphates  as  under 
"Zinc  Lead." 

Xitrogen.  —  Determine  by  the  Kjeldahl-Gunning 
method. 


306  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

PRUSSIAN  BLUE 

Hygroscopic  Moisture. — Determine  on  a  i  g.  sample 
by  heating  for  2  hours  at  105°  C. 

Water  of  Composition.  —  Determine  by  difference  after 
the  other  constituents  have  been  obtained. 

Ferrocyanic  Acid.1  --Treat  0.5  g.  with  10  c.c.  of  nor- 
mal potassium  hydroxid  solution  in  a  flask.  Boil  for  5 
minutes,  dilute  with  50  c.c.  of  hot  water,  filter,  and 
wash  the  ferric  hydroxid. 

The  nitrate  containing  a  solution  of  potassium  fer- 
rocyanide  is  slightly  acidified  with  sulphuric  acid,  2  to  3 
g.  of  ammonium  persulphate  are  added,  and  the  liquid 
boiled  from  20  to  30  minutes.  Any  blue  color  which 
persists  is  removed  by  the  addition  of  hydrochloric  acid 
and  a  little  more  persulphate. 

The  iron  is  precipitated  with  ammonia  by  the  usual 
method  gravimetrically  or  volumetrically.  Calculate  as 
FeC6N6. 

Cyanogen.  —  If  desired,  the  total  nitrogen  in  Prussian 
blue  may  be  determined  by  the  Kjeldahl-Gunning  method 
as  outlined  in  Bulletin  107,  Bureau  of  Chemistry,  U.  S. 
Dept.  of  Agriculture. 

To  determine  the  amount  of  Prussian  blue,  multiply 
the  total  iron  content  by  3.03  or  nitrogen  content  by  4.4. 
The  results  thus  obtained  are  fairly  approximate.  They 
are  not  exact  since  the  composition  of  Prussian  blue  is 
variable.  The  pure  Prussian  blue  should  contain  about 
20  per  cent  of  nitrogen  and  30  per  cent  of  iron,  and  less 
than  7  per  cent  of  moisture.  The  sulphuric  acid  used  in 
determining  the  nitrogen  by  the  Kjeldahl-Gunning  method 
should  not  be  blackened  due  to  the  presence  of  organic 
adulterants. 

1  Ber.  1903,  36,  1929. 


ANALYSIS  OF  PAINT  MATERIALS  307 

Iron.  —  To  determine  the  total  iron  in  Prussian  blue, 
ignite  i  g.  gently  until  the  blue  color  is  completely  dis- 
charged. Dissolve  the  residue  in  10  c.c.  of  hydrochloric 
acid  (i :  i),  filter,  make  up  to  100  c.c.  in  a  graduated  flask. 
Determine  Fe203  in  50  c.c.  in  this  solution  (calculate  to 
metallic  iron). 

In  the  other  50  c.c.  of  the  filtrate  determine  Fe2O3  + 
A12O3  by  the  usual  methods.  Calculate  A12O3  by  difference. 
Report  as  metallic  aluminium. 

Calcium. — Determine  as  usual  in  the  filtrate  from 
Fe2O3  +  A12O3. 

Alkali  Metals.  —  Determine  by  the  usual  methods. 

ANALYSIS  OF  ULTRAMARINE 


The  ultramarine  is  finely  powdered  and  dried  at  100°. 
2  to  10  g.  are  weighed  off,  digested  with  water,  filtered, 
the  filtrate  diluted  to  500  c.c.,  and  100  c.c.  taken  for  each 
of  the  following  determinations. 

(a)  Na2S2O3  —  determine  with  iodine  solution  and 
starch.  Calculate  to  Na2S2O3  +  Ag. 

(6)  Na2SO4  —  determine  by  precipitating  with  barium 
chloride  in  acid  solution. 

(c)  NaCl  —  determine  by  precipitating  with  AgN03 
(NaCl  is  rarely  present  in  ultramarine). 

10  to  20  grams  of  ultramarine  are  washed  two  or  three 
times  by  decantation  (to  obtain  a  clear  filtrate,  alcohol  is 
added).  Evaporate  almost  to  dryness  with  a  dilute  solu- 
tion of  sodium  sulphite l  on  the  water  bath.  Wash  until 
a  test  of  the  ultramarine  moistened  with  water  and  fil- 
tered gives  no  trace  of  turbidity  with  barium  chloride. 

1  In  order  to  remove  free  S,  for  CS2  extracts  only  40  to  60% 
of  the  same. 


308  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

The  ultramarine  dried  at  130  to  140°  is  again  powdered 
and  placed  hot  into  a  glass  stoppered  flask. 

II 

Estimation  of  silicic  acid,  silica,  clay  and  total  sulphur. 

i  g.  of  the  dried  substance  is  weighed  into  a  porcelain 
dish,  stirred  up  with  water  and  treated  with  i  to  2  c.c.  of 
bromine.  If  it  is  partially  dissolved  (as  shown  by  the  yellow 
coloration  of  the  liquid)  15  to  20  c.c.  of  nitric  acid  are  added 
and  the  whole  evaporated  to  dryness  on  the  water  bath. 

Take  up  with  water,  add  20  c.c.  of  hydrochloric  acid 
and  evaporate  again  (to  remove  nitric  acid  which  would 
increase  the  BaSO4  precipitate,  and  to  render  silicic  acid 
insoluble).  Treat  with  hydrochloric  acid,  digest  warm 
for  a  few  hours,  dilute  with  water  and  filter.  On  the 
filter  are  left  silicic  acid  and  sand. 

To  determine  total  sulphur,  the  filtrate  is  heated  to 
boiling  and  precipitated  with  barium  chloride. 

Ill 

• 

Estimation  of  alumina  and  of  soda. 

i  g.  of  ultramarine,  washed  and  dried  as  in  number 
I,  is  carefully  mixed  with  water  and  treated  with  an  ex- 
cess of  hydrochloric  acid.  After  standing  for  a  while  it 
is  heated  until  the  solution  settles  clear.  It  is  then  fil- 
tered, leaving  sulphur,  sand  and  silicic  acid  undissolved. 
The  residue  is  weighed  after  ignition.  The  filtrate  is 
evaporated  to  dryness,  the  residue  moistened  with  water 
and  hydrocloric  acid  and  again  dried.  Take  up  with 
hydrochloric  acid,  dilute  with  water  after  standing  for 
some  time  and  filter.  On  the  filter  is  left  silicic  acid, 
which,  added  to  the  residue  obtained  in  the  first  filtra- 
tion, gives  the  content  of  total  silicic  acid  and  sand.  The 
filtrate  is  evaporated  to  dryness  to  remove  excess  hydro- 


ANALYSIS  OF  PAINT  MATERIALS  309 

chloric  acid.  The  residue  is  dissolved  in  water,  precipi- 
tated with  ammonia  and  the  whole  thoroughly  dried  in 
the  water  bath.  (This  facilitates  complete  washing  of 
the  alumina.) 

Take  up  the  residue  with  hot  water,  add  a  few  drops 
of  ammonia,  heat  and  filter.  Alumina  on  the  filter  is 
determined  and  weighed. 

For  determining  soda,  the  filtrate  is  treated  with  sul- 
phuric acid  and  a  little  fuming  nitric  acid  and  evaporated 
to  dryness.  The  residue  is  strongly  ignited  and  the 
Na2SO4  calculated  to  Na. 


(Carbon  Black,  Lampblack,  Vine  Black,  Bone  Black) 

Moisture.  —  Determine  on  a  2  g.  sample  by  heating 
for  two  hours  at  105°  C. 

Volatile.  —  Heat  for  10  minutes  over  a  Bunsen  flame 
in  a  well-covered  porcelain  crucible. 

Ash.  —  Determine  on  a  i  g.  sample,  ignite  over  a 
Bunsen  burner  with  free  access  of  air.  When  the  ash  is 
large  in  quantity,  cool,  moisten  with  a  solution  of  ammo- 
nium carbonate  and  ignite  again  gently. 

Soluble  and  Insoluble  Ash. — Treat  the  ash  obtained 
by  the  above  procedure  with  5  to  10  c.c.  of  dilute  hydro- 
chloric acid,  heat,  filter,  wash  and  weigh  the  insoluble 
portion.  Calculate  the  percentage  of  acid-soluble  ash 
from  the  total  ash  and  the  acid-insoluble  ash. 

Certain  blacks  are  sometimes  adulterated  with  Prus- 
sian blue.  To  detect  the  latter,  boil  with  dilute  caustic 
soda,  filter,  acidify  the  filtrate  with  dilute  hydrochloric 
acid,  and  add  a  mixture  of  ferric  chloride  and  ferrous 
sulphate.  The  formation  of  a  blue  precipitate  indicates 
the  presence  of  Prussian  blue. 


310  CHEMISTRY  AND  TECHNOLOGY  OF  PAINTS 

GRAPHITE 

Heat  i  g.  of  the  finely  powdered  graphite  to  a  dull 
red  heat  and  calculate  the  loss  in  weight  as  water.  The 
dried  substance  is  intimately  mixed  with  3  g.  of  a  mixture 
of  equivalent  parts  of  K2C03  and  Na2C03  and  placed  in  a 
crucible,  i  g.  of  KOH  or  NaOH  is  sprinkled  over  the 
surface  of  this  mixture  and  the  whole  heated  slowly  to 
redness.  The  mass  fuses,  swells  and  forms  a  crust  on  top, 
which  must  be  broken  with  a  stout  platinum  wire. 

After  fusing  for  one  half  hour,  the  melt  is  cooled, 
heated  with  water  for  J  hour  almost  to  boiling,  filtered, 
washed  well  and  the  liquids  set  aside.  The  insoluble  is 
dried,  placed  in  a  dish,  the  filter  ash  added  and  about  3  g. 
of  HC1  (specific  gravity  1.18)  poured  in.  After  several 
minutes  a  slight  gelatinization  sets  in  due  to  the  decom- 
position of  the  small  residue  of  alkali  silicate.  The  addi- 
tion of  a  little  more  hydrochloric  acid  brings  the  silicic 
acid  into  solution.  After  digestion  for  one  hour,  dilute 
with  water,  filter  and  wash  out.  The  residue  on  the  fil- 
ter is  pure  carbon,  which,  after  drying  and  gentle  ignition, 
is  weighed.  The  acid  filtrate  is  united  with  the  alkaline 
one  obtained  above,  more  HC1  added  until  weakly  acid, 
evaporated  to  dry  ness,  and  silicic  acid,  alumina  and  iron 
oxid  determined  as  usual. 

BLANC  FIXE 

Water  Soluble  Salts.  —  Owing  to  the  variety  of  methods 
employed  in  the  technical  production  of  blanc  fixe,  a 
preliminary  qualitative  examination  of  the  material  is 
always  essential  before  proceeding  with  the  quantitative 
analysis. 

Digest  about  5  g.  with  150  c.c.  of  hot  water  and 
filter.  Examine  the  filtrate  to  detect  the  presence  of 


ANALYSIS  OF  PAINT  MATERIALS  311 

water    soluble  salts.     Determine    the    amount    of   water 
soluble  salts,  by  difference,  on  a  i  g.  sample. 

Acid  Soluble. —  Digest  i  g.  of  blanc  fixe  with  hot  water, 
wash  by  decantation  and  filter,  keeping  as  much  of  the 
residue  as  possible  in  the  beaker.  Discard  the  filtrate 
and  treat  the  residue  in  the  beaker  with  about  25  c.c.  of 
hot  dilute  HC1  (1:3);  filter  through  the  filter  paper  used 
above,  wash  and  ignite.  Add  i  drop  of  nitric  and  2  drops 
of  sulphuric  acid,  evaporate,  ignite  again  and  weigh.  Cal- 
culate %  acid  soluble  from  loss  in  weight,  %  water  soluble 
and  %  moisture. 

BaSCX —  Proceed  as  outlined  below  under  barytes 
(fusion  in  platinum  with  Na2C03)  to  determine  barium 
sulphate  and  silica  (Page  314). 

Iron.  —  Determine  colorimetrically. 

Silica.  —  To  determine  qualitatively l  whether  a  sample 
of  blanc  fixe  is  free  from  silica  or  clay,  heat  about  0.5  g. 
with  10  to  15  c.c.  of  concentrated  sulphuric  acid.  A  pure 
blanc  fixe  or  barytes  dissolves  completely.  Silicious  matter 
remains  undissolved.  Determine  the  amount  of  silicious 
matter  on  a  i.  g.  sample  by  evaporating  with  a  few  c.c. 
of  hydrofluoric  acid  and  several  drops  of  sulphuric  acid. 

ANALYSIS  OF  WHITING 

Carbon  Dioxid.  —  Determined  as  outlined  under  "  White 
Lead." 

Calcium.  —  Determined  by  the  usual  methods, 

GYPSUM  OR  CALCIUM  SULPHATE 

Calcium  and  Sulphates.  —  Determine  by  the  usual 
methods. 

Moisture.  --Dry  2  g.  in  a  vacuum  dessicator  over 
sulphuric  acid  to  constant  weight. 

1  Method  developed  in  the  laboratory  of  Toch  Brothers. 


312  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Combined  H20  and  Moisture.  —  Heat  i  g.  in  a  covered 
porcelain  crucible  on  an  asbestos  plate  for  15  minutes, 
then  heat  the  bottom  of  the  crucible  to  dull  redness  for 
10  minutes  over  a  Bunsen  burner,  remove  the  cover  and 
heat  for  30  minutes  at  a  slightly  lower  temperature. 
Cool  and  weigh  rapidly. 

SILICA,  ASBESTINE,  CLAY  (BARYTES) 

Hygroscopic  Moisture.  —  Determine  on  a  2  g.  sample 
by  heating  for  i  hour  at  105°  C. 

Loss  on  Ignition.  — Determine  on  a  i  g.  sample.  This 
is  largely  water  of  composition,  unless  carbonates  are 
present. 

Complete  Analysis.  —  Mix  0.5  g.  in  a  platinum  crucible 
intimately  writh  about  5  g.  of  anhydrous  sodium  car- 
bonate. Add  a  thin  layer  of  the  latter  on  top,  cover 
the  crucible  and  heat  gently  over  a  Tirrill  or  Tech  burner 
for  a  short  time.  Raise  the  temperature  gradually  to 
the  full  heat  of  the  burner.  Finally  heat  for  a  short 
time  over  the  blast  lamp.  Allow  to  cool,  then  heat  the 
lower  part  of  the  crucible  to  dull  redness,  and  cool  again. 
Add  a  little  water,  heat  carefully  to  boiling  and  the  melt 
will  readily  separate  from  the  crucible.  Place  the  melt 
in  an  evaporating  dish;  wash  the  crucible  with  a  little ~ 
hot  water,  and  add  to  the  dish.  If  barytes,  or  blanc  fixe 
is  present,  the  melt  is  digested  with  hot  water  until 
completely  disintegrated,  the  barium  carbonate  is  fil- 
tered off  and  washed,  and  the  barium  determined  as 
outlined  under  barium  carbonate.  The  filtrate  is  then 
treated  in  a  large  covered  beaker  with  concentrated 
hydrochloric  acid.  After  a  certain  amount  of  acid  has 
been  added,  the  silicic  acid  separates  out  as  a  gelatinous 
mass,  which  has  to  be  broken  up  in  order  to  obtain  inti- 
mate admixture  with  the  acid.  After  an  excess  of  acid 


ANALYSIS  OF  PAINT  MATERIALS  313 

has  been  added,  the  solution  is  heated  to  boiling,  trans- 
ferred to  a  porcelain  or  platinum  dish  and  evaporated  to 
dryness. 

It  is  essential  that  dehydration  of  the  silica  be  carried 
out  twice1  at  the  temperature  of  the  steam  bath  and  that 
the  insoluble  silica  be  filtered  off  before  evaporating  the 
second  time. 

Filter,  wash,  combine  the  insoluble  residues  from  the 
two  dehydrations,  ignite  in  a  platinum  crucible  and  weigh. 
Drive  off  Si02  with  a  few  c.c.  of  HF  and  several  drops  of 
H2SO4.  Ignite  and  reweigh.  The  loss  in  weight  is  silica. 

Iron  and  Aluminium  Oxids.  —  Treat  the  filtrate  from 
the  silicic  acid  with  a  few  drops  of  concentrated  nitric 
acid  and  10  to  20  c.c.  of  a  cold  saturated  solution  of 
ammonium  chloride.  Heat  to  boiling  and  precipitate 
with  a  slight  excess  of  ammonia.  Allow  the  precipitate 
to  settle,  filter  off  the  clear  liquid  and  wash  twice  by 
decantation  with  hot  water.  Redissolve  the  ferric  and 
aluminium  hydroxids  by  running  hot  dilute  hydrochloric 
acid  through  the  filter  paper  into  the  beaker  containing 
the  major  portion  of  the  precipitate.  Reprecipitate  with 
ammonia,  as  before,  filter,  wash  and  ignite  wet  in  the 
platinum  crucible  containing  the  residue  obtained  after 
SiO2  was  volatilized  with  HF  and  H2SO4.  Weigh  as 
Fe2O3  +  A12O3. 

For  the  determination  of  iron  in  the  mixed  oxids,  sse 
Treadwell  and  Hall,  Vol.  II,  p.  109. 

Calcium.  —  Evaporate  the  filtrates  from  the  ferric  and 
aluminium  hydroxids  to  a  small  volume.  Heat  to  boil- 
ing and  precipitate  with  a  boiling  solution  of  ammonium 
oxalate.  Allow  to  stand  for  several  hours.  Filter  and 
wash.  Puncture  the  filter  paper  with  a  glass  rod,  wash  the 
precipitate  into  a  beaker  with  a  stream  of  water  from  the 
1  Hillebrand,  "Analysis  of  Silicate  and  Carbonate  Rocks." 


314  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

wash  bottle,  and  pass  20  c.c.  of  hot  .dilute  sulphuric  acid 
(1:1)  over  and  through  the  filter  paper.  Heat  to  90°  C. 
and  titrate  with  N/io  KMn04. 

Magnesium.  —  Evaporate  the  filtrate  from  the  calcium 
oxalate  to  dryness,  and  ignite  in  a  porcelain  dish.  Moisten 
the  residue  with  a  little  concentrated  hydrochloric  acid 
and  dissolve  in  hot  water.  Filter  and  determine  mag- 
nesium in  the  filtrate.  Heat  to  boiling  and  treat  with  an 
excess  of  sodium  or  ammonium  phosphate.  Add  an 
amount  of  10  per  cent  ammonia  equal  to  \  of  the  volume  of 
solution.  Allow  to  cool  and  set  aside  for  a  few  hours. 
Filter  through  an  alundum  crucible,  wash  with  2.5  per  cent 
ammonia,  dry,  ignite  slowly  at  first  and  finally  strongly 
until  the  precipitate  is  white.  Weigh  as  Mg2P2O7. 

Alkalies.  --  See  J.  Lawrence  Smith  (Bulletin  422,  U. 
S.  Geologic  Survey). 

BARYTES 

Make  a  preliminary  test  for  lead  compounds.  In 
the  absence  of  the  latter  weigh  off  i  g.  sample  and  mix 
with  5  g.  anhydrous  sodium  carbonate  in  a  platinum 
crucible.  Fuse  over  the  blast  lamp  for  a  half  hour,  occa- 
sionally imparting  a  rotary  motion  to  the  crucible  to 
insure  thorough  reaction.  Allow  to  cool,  then  heat  the 
lower  part  of  the  crucible  to  dull  redness,  and  cool  again. 
Add  a  little  water,  bring  carefully  to  boil,  and  the  melt 
will  readily  separate  from  the  crucible.  Place  in  an 
evaporating  dish,  add  100  c.c.  of  water,  and  digest  on 
the  steam  bath  until  completely  disintegrated.  Filter 
and  wash  the  insoluble  residue  (BaCO3)  until  free  from 
soluble  salts.  Dissolve  the  BaCO3  with  25  c.c.  of  hydro- 
chloric acid  (1:3),  catching  the  filtrate  and  passing  it 
through  the  filter  to  insure  complete  solution  of  the 
barium  carbonate.  Boil  to  expel  carbon  dioxid,  neu- 


ANALYSIS  OF  PAINT  MATERIALS  315 

tralize  the  filtrate  with  ammonia,  reacidify  with  a  few 
drops  of  hydrochloric  acid,  heat  to  boiling,  and  precipi- 
tate with  dilute  sulphuric  acid.  Filter  and  wash  on  a 
Gooch  crucible,  dry  at  130°  C.  and  report  as  BaSO4. 

In  the  presence  of  lead,  first  extract  the  barytes  with 
hot  concentrated  ammonium  acetate  solution  before 
proceeding  with  the  sodium  carbonate  fusion,  since  the 
presence  of  metallic  lead  in  the  fusion  will  ruin  the 
platinum  crucible. 

Iron.  —  Determine  colorimetrically. 

Clay  and  Silica.  —  Acidify  the  filtrate  from  the  barium 
carbonate  with  hydrochloric  acid,  evaporate  to  dryness 
on  the  steam  bath,  heat  for  20  minutes  longer  on  the 
steam  bath,  and  extract  with  hot  water  and  a  little 
hydrochloric  acid.  Filter,  wash  and  weigh*  the  insoluble 
SiOo.  Determine  alumina  in  the  filtrate  from  SiO2  as 
usual.  See  also  determination  of  silica  in  blanc  fixe 

(P-  311)- 

In  reporting  the  presence  of  silica  and  alumina,   it 

must  be  remembered  that  the  reagents  used  in  the  above 
determination,  sodium  carbonate  and  ammonia,  almost 
always  contain  appreciable  quantities  of  silica  and  alu- 
mina. Especially  is  this  true  of  aqua  ammonia,  except 
when  kept  in  bottles  lined  with  ceresin  or  paraffin  wax. 

ANALYSIS  OF  BARIUM  CARBONATE 

Water  Soluble  Salts.  --Determine  by  difference  in  a  i 
g.  sample,  treat  with  hot  water,  filter,  wash,  and  weigh 
the  insoluble. 

Insoluble.  --  Dissolve  about  10  g.  in  dilute  hydro- 
chloric acid.  Heat  to  boiling,  filter,  wash  and  weigh 
the  insoluble  residue.  The  latter  is  generally  silicious, 
but  should  be  examined  to  determine  the  presence  of 
barium. 


3l6  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Barium.  --Dissolve  0.5  g.  in  dilute  hydrochloric  acid, 
neutralize  with  ammonia,  then  reacidify  faintly  with 
hydrochloric  acid.  Dilute  to  100  c.c.,  heat  to  boiling, 
and  precipitate  with  hot  dilute  sulphuric  acid.  Filter  on 
a  Gooch  crucible,  wash,  and  dry  at  130°  C.  Calculate 
BaSO4  to  BaC03.  For  the  separation  of  barium,  cal- 
cium, and  strontium  from  each  other,  see  Treadwell  and 
Hall,  Anal.  Chem.,  Vol.  II,  p.  79. 

Carbon  Dioxid.  —  Determine  by  evolution  as  outlined 
under  "White  Lead." 

Iron.1 — Treat  2  g.  in  a  beaker  with  15  c.c.  of  water 
and  sufficient  nitric  acid  to  dissolve  the  barium  carbonate. 
Boil  for  several  minutes  to  expel  carbon  dioxid  and  to 
convert  all  the  iron  to  the  ferric  state.  Filter  and 
wash  the  residue.  Cool  the  nitrate,  neutralize  with 
ammonia  and  acidify  faintly  with  nitric  acid. 

Wash  the  contents  of  the  beaker  into  a  100  c.c. 
Nessler  cylinder,  add  15  c.c.  of  dilute  ammonium  thio- 
cyanate  (1:20)  and  dilute  to  the  mark.  The  depth  of  the 
blood  red  color  developed  is  a  measure  of  the  amount  of 
iron  present.  Compare  with  a  blank  made  as  follows: 

Prepare  a  standard  solution  of  ferric  ammonium  sul- 
phate by  dissolving  0.7022  g.  of  ferrous  ammonium  sul- 
phate in  water.  Acidify  with  sulphuric  acid,  heat  to 
boiling  and  oxidize  the  iron  by  the  addition  of  a  solu- 
tion of  potassium  permanganate.  Only  the  faintest 
excess  of  permanganate  should  be  added.  The  faint  pink 
tinge  due  to  the  latter  soon  disappears.  The  solution  is 
cooled  and  diluted  to  i  liter.  One  c.c.  of  this  solution 
is  equivalent  to  o.oooi  g.  of  iron. 

Into  a  100  c.c.  Nessler  cylinder  add  about  the  same 
amount  of  nitric  acid  as  was  used  to  dissolve  the  barium 

1  Modified  Thompson  &  Schaeffer  method.  J.  Ind.  Eng.  Chem. 
1912,  659. 


ANALYSIS  OF  PAINT  MATERIALS  317 

carbonate,  and  15  c.c.  of  ammonium  thiocyanate  solution. 
Dilute  to  100  c.c.  and  add  the  standard  ferric  ammonium 
sulphate  solution,  drop  by  drop,  until  the  color  exactly 
matches  that  developed  in  the  sample  being  tested. 
One  c.c.  of  the  solution  is  equivalent  to  o.oi  per  cent 
iron  when  a  i  g.  sample  is  used.  Not  more  than 
2  or  3  c.c.  of  the  standard  should  be  required  to  equal 
the  color;  otherwise,  the  color  becomes  too  deep  for 
comparison. 

Sulphur. —  For  colorimetric  determination  see  Tread- 
well  &  Hall,  Vol.  II,  pages  354-7. 

Chlorine.  —  Determine  in  the  water  soluble  portion 
(acidified  with  nitric  acid)  by  precipitating  hot  in  the 
presence  of  a  slight  excess  of  silver  nitrate,  filter  on  a 
Gooch  or  alundum  crucible,  wash,  and  weigh  the  insoluble 
AgCl  after  drying  at  130°  C. 

ANALYSTS  OF  MIXED  WHITE  PAINTS 
I.   By  use  of  Acetic  Acid 

Treat  i  g.  of  the  mixed  white  pigment  with  22  c.c.  of 
water  and  10  c.c.  of  glacial  acetic  acid.  Boil,  filter,  and 
wash  with  water.  The  filtrate  is  heated  to  boiling,  and 
precipitated  with  hydrogen  sulphide.  Filter  off  the  lead 
and  zinc  sulphides,  dissolve  in  hot  dilute  nitric  acid,  and 
determine  lead  and  zinc  as  usual.  Calculate  the  lead  to 
white  lead,  and  zinc  to  oxid.  The  filtrate  from  lead  and 
zinc  sulphides  is  tested  for  Ba,  Ca,  and  Mg.  Determine 
and  calculate  to  carbonates. 

To  the  residue  from  the  acetic  acid  treatment  add 
10  c.c.  of  water,  10  c.c.  of  strong  hydrochloric  acid,  and 
5  g.  ammonium  chloride.  Heat  on  steam  bath  for  5 
minutes,  dilute  with  boiling  water  to  400  c.c.,  boil,  filter, 
wash,  ignite  and  weigh  the  insoluble.  Examine  for 
silica,  clay,  barytes  or  asbestine. 


3i8  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Precipitate  the  lead  in  the  filtrate  with  hydrogen  sul- 
phide, filter  and  wash.  Dissolve  in  hot  dilute  nitric  acid, 
and  determine  as  usual.  Report  as  PbSO4.  The  fil- 
trate is  boiled  to  expel  hydrogen  sulphide,  a  few  drops 
of  nitric  acid,  ammonium  chloride,  and  ammonia  in  excess 
are  added  to  precipitate  iron  and  aluminium.  Calcium 
is  determined  in  the  filtrate  as  usual.  Report  as  CaS04. 

II.  By  G.  W.  Thompson,  (Jour.  Soc.  Chem.  Ind.  15,  432) 
"The  qualitative  examination  for  the  elements  pres- 
ent may  be  determined  as  follows:  Effervescence  with 
concentrated  hydrochloric  acid  indicates  carbonic  acid, 
sulphuretted  hydrogen  if  zinc  sulphide  is  present,  or  sul- 
phurous acid  if  lead  sulphite  is  present.  These  latter 
two  may  be  recognized  by  their  odors.  Boil  a  portion 
of  the  paint  with  acid  ammonium  acetate  and  test  a 
portion  of  the  filtrate  for  sulphuric  acid  with  barium 
chloride.  Test  another  portion  of  the  same  solution 
with  sulphuric  acid  in  excess  for  lead  and  test  filtrate 
for  zinc  by  making  alkaline  with  ammonia,  and  adding 
ammonium  sulphide.  Test  another  portion  of  the  am- 
monium acetate  solution  for  lime  by  making  alkaline 
with  ammonia,  adding  ammonium  sulphide,  filtering  and 
adding  ammonium  oxalate  to  filtrate.  The  portion 
insoluble  in  ammonium  acetate,  in  the  absence  of  sul- 
phite of  zinc  and  sulphate  of  lead  may  be  barytes,  China 
clay,  or  silica.  The  qualitative  examination  of  this 
residue  is  best  combined  with  quantitative  examination 
given  further  on." 

"The  oxids  and  elements,  the  presence  of  which  is 
usually  possible  in  a  white  paint,  are:  carbonic  acid, 
water  (combined),  sulphuric  acid,  sulphurous  acid,  sulphur 
(combined  as  sulphide),  silica,  barium  oxid,  calcium 
oxid,  zinc  oxid,  and  zinc  combined  as  sulphide,  lead 
oxid,  aluminium  oxid." 


ANALYSIS  OF  PAINT  MATERIALS  319 

"In  the  absence  of  sulphuric  acid,  the  lead  soluble  in 
acetic  acid  may  be  directly  calculated  to  white  lead." 

"Sulphuric  acid  may  exist  in  two  conditions,  in  one 
it  is  soluble  in  ammonium  acetate,  and  in  the  other,  as 
in  barytes,  it  is  insoluble  in  ammonium  acetate.  That 
soluble  in  ammonium  acetate  may  be  determined  by 
precipitating  with  barium  chloride  in  that  solution. 
Sulphuric  acid  in  barytes  is  best  calculated  from  the 
barium  present,  and  determined  as  described  later  on. 
Sulphurous  acid  may  be  determined  by  oxidation  to  sul- 
phuric acid,  or  its  determination  may  be  based  on  the 
insolubility  of  lead  sulphite  in  ammonium  acetate.  For 
instance,  one  portion  of  the  sample  is  oxidized  with 
nitric  acid  and  the  total  lead  determined.  Another 
portion  is  treated  directly  with  ammonium  acetate,  and 
the  lead  soluble  in  that  menstruum  determined.  The 
difference  between  the  two  determinations  is  the  lead 
present  as  sulphite,  from  which  we  may  calculate  the 
sulphurous  acid  present.  Sulphur  as  sulphide  is  always 
present  as  zinc  sulphide,  which  is  never  used  in  the 
presence  of  lead  compounds.  It  may  be  determined  by 
oxidation  with  bromine  water  and  precipitation  with 
barium  chloride,  or  by  determining  the  zinc  insoluble 
in  ammonium  acetate.  Silica  may  be  determined  by 
treating  the  matter  insoluble  in  ammonium  acetate  with 
hydrofluoric  acid  and  sulphuric  acid.  The  loss  on 
ignition  is  silica,  or  it  may  be  determined  by  fusing  the 
residue  in  the  regular  way.  Barium  oxid  is  determined 
by  precipitation  with  sulphuric  acid  from  hydrochloric 
acid  solution  of  that  part  of  fused  residue  insoluble  in 
water." 

RAPID  METHODS  FOR  WHITE  PIGMENTS 

"Sample  i  is  a  mixture  of  barytes,  white  lead,  and 
zinc  oxid. 


320  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

"Two  i-gram  portions  are  weighed  out.  One  is 
dissolved  in  acetic  acid  and  filtered,  the  insoluble  matter 
ignited  and  weighed  as  barytes,  the  lead  in  the  soluble 
portion  precipitated  with  dichromate  of  potash,  weighed 
in  Gooch  crucible  as  chromate,  and  calculated  to  white 
lead. 

"The  other  portion  is  dissolved  in  dilute  nitric  acid, 
sulphuric  acid  added  in  excess,  evaporation  carried  to 
fumes,  water  added,  the  zinc  sulphate  solution  filtered 
from  barytes  and  lead  sulphate  and  precipitated  directly 
as  carbonate,  filtered,  ignited,  and  weighed  as  oxid. 

"Sample  2  is  a  mixture  of  barytes  and  so-called  sub- 
limed white  lead. 

"Weigh  out  three  i-gram  portions.  In  one  determine 
zinc  oxid  as  in  Case  i.  Treat  a  second  portion  with 
boiling  acetic  acid,  filter,  determine  lead  in  filtrate  and 
calculate  to  lead  oxid.  Treat  third  portion  by  boiling 
with  acid  ammonium  acetate,  filter,  ignite,  and  weigh 
residue  as  barytes,  determine  total  lead  in  filtrate,  deduct 
from  it  the  lead  as  oxid,  and  calculate  the  remainder 
to  sulphate.  Sublimed  lead  contains  no  hydrate  of  lead, 
and  its  relative  whiteness  is  probably  due  to  the  oxid  of 
lead  being  combined  with  the  sulphate  as  basic  sulphate. 
Its  analysis  should  be  reported  in  terms  of  sulphate  of 
lead,  oxid  of  lead,  and  oxid  of  zinc. 

"Sample  3  is  a  mixture  of  barytes,  sublimed  lead,  and 
white  lead. 

"Determine  barytes,  zinc  oxid,  lead  soluble  in  acetic 
acid  and  in  ammonium  acetate,  as  in  Case  2;  also  deter- 
mine carbonic  acid,  which  calculate  to  white  lead,  deduct 
lead  in  white  lead  from  the  lead  soluble  in  acetic  acid,  and 
calculate  the  remainder  to  lead  oxid. 

"Sample  4  is  a  mixture  of  barytes,  white  lead,  and 
carbonate  of  lime. 


ANALYSIS  OF  PAINT  MATERIALS  321 

"Determine  barytes  and  lead  soluble  in  acetic  acid 
(white  lead)  as  in  Case  i.  In  filtrate  from  lead  chromate 
precipitate  lime  as  oxalate,  weigh  as  sulphate,  and  cal- 
culate to  carbonate.  Chromic  acid  does  not  interfere 
with  the  precipitation  of  lime  as  oxalate  from  acetic  acid 
solution. 

"Sample  5  is  a  mixture  of  barytes,  white  lead,  zinc 
oxid,  and  carbonate  of  lime. 

"Determine  barytes  and  white  lead  as  in  Case  i. 
Dissolve  another  portion  in  acetic  acid,  filter  and  pass 
sulphuretted  hydrogen  through  the  boiling  solution,  filter, 
and  precipitate  lime  in  filtrate  as  oxalate;  dissolve  mixed 
sulphides  of  lead  and  zinc  in  dilute  nitric  acid,  evaporate 
to  fumes  with  sulphuric  acid,  separate,  and  determine 
zinc  oxid  as  in  Case  i. 

"Sample  6  is  a  mixture  of  barytes,  white  lead,  sub- 
limed lead,  and  carbonate  of  lime. 

"Determine  barytes,  lead  soluble  in  acetic  acid  and  in 
ammonium  acetate,  as  in  Case  2,  lime  and  zinc  oxid,  as 
in  Case  5,  and  carbonic  acid.  Calculate  lime  to  car- 
bonate of  lime,  deduct  carbonic  acid  in  it  from  total 
carbonic  acid,  calculate  the  remainder  of  it  to  white  lead, 
deduct  lead  in  white  lead  from  lead  soluble  in  acetic  acid, 
and  calculate  the  remainder  to  oxid  of  lead. 

"Sample  7  contains  sulphate  of  lime. 

"Analyses  of  paints  containing  sulphate  of  lime 
present  peculiar  difficulties  from  its  proneness  to  give 
up  sulphuric  acid  to  lead  oxid  if  white  lead  is  present. 
Sulphate  of  lime  and  white  lead  boiled  in  water  are  more 
or  less  mutually  decomposed  with  the  formation  of  sul- 
phate of  lead  and  carbonate  of  lime.  A  method  for  the 
determination  of  sulphate  of  lime  is  by  prolonged  washing 
with  water  with  slight  suction  in  a  weighed  Gooch 
crucible.  This  is  exceedingly  tedious,  but  thoroughly 


322  .    CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

accurate.  A  reservoir  containing  water  may  be  placed 
above  the  crucible,  and  the  water  allowed  to  drop  slowly 
into  it.  This  may  take  one  or  two  days  to  bring  the 
sample  to  constant  weight,  during  which  time  several 
liters  of  water  will  have  passed  through  the  crucible. 
Another  method  for  separating  the  sulphate  of  lime  is 
by  treatment  in  a  weighed  Gooch  crucible  with  a  mixture 
of  nine  parts  of  95  per  cent  alcohol  and  one  part  of 
glacial  acetic  acid.  Acetates  of  lead,  zinc,  and  lime  being 
soluble  in  this  mixture,  the  residue  contains  all  the  sul- 
phate of  lime  and  any  sulphate  of  lead  and  barytes  which 
may  be  present.  Determine  the  lead  and  lime  as  in 
sample  4,  and  calculate  to  sulphates.  Sulphate  of  lime 
should  be  fully  hydrated  in  paints.  To  determine  this, 
obtain  loss  on  ignition;  deduct  carbonic  acid  and  water 
in  other  constituents;  the  remainder  should  agree  fairly 
well  with  the  calculated  water  in  the  hydrated  sulphate 
of  lime,  if  it  is  fully  hydrated.  If,  after  washing  a  small 
portion  of  the  sample  with  water,  the  residue  shows  no 
sulphuric  acid  soluble  in  ammonium  acetate,  the  sulphate 
of  lime  may  be  obtained  by  determining  the  sulphuric 
acid  soluble  in  ammonium  acetate  and  calculating  to 
sulphate  of  lime.  The  difficulty  is  in  determining  the  sul- 
phate of  lime  in  the  presence,  or  possible  presence,  of 
sulphate  of  lead.  To  illustrate  the  analysis  of  sample  of 
white  paint  containing  sulphate  of  lime  and  the  difficulty 
attending  thereon,  we  would  mention  a  sample  containing 
sublimed  lead,  white  lead,  carbonate  of  lime,  and  sulphate 
of  lime.  In  such  a  sample  we  would  determine  the 
lead,  lime,  sulphuric  acid,  carbonic  acid,  loss  on  ignition, 
the  portion  soluble  in  water,  and  the  lime  or  sulphuric 
acid  in  that  portion,  calculating  to  sulphate  of  lime. 
Deduct  the  lime  in  the  sulphate  of  lime  from  the  total 
lime,  and  calculate  the  remainder  to  carbonate  of  lime; 


ANALYSIS  OF  PAINT  MATERIALS  323 

deduct  the  carbonic  acid  in  the  carbonate  of  lime  from 
the  total  carbonic  acid,  and  calculate  the  remainder  to 
white  lead;  deduct  the  sulphuric  acid  in  the  sulphate  of 
lime  from  the  total  sulphuric  acid,  and  calculate  the 
remainder  to  sulphate  of  lead.  The  lead  unaccounted  for 
as  sulphate  or  white  lead  is  present  as  oxid  of  lead. 
Deduct  the  carbonic  acid  and  water  in  the  carbonate  of 
lime  and  white  lead  from  the  loss  on  ignition,  the  re- 
mainder being  the  water  of  hydration  of  the  sulphate  of 
lime. 

"Sample  8  contains  as  insoluble  matter,  barytes, 
China  clay  and  silica. 

"  After  igniting  and  weighing  the  insoluble  matter, 
carbonate  of  soda  is  added  to  it,  and  the  mixture  fused. 
The  fused  mass  is  treated  with  water,  and  the  insoluble 
portion  filtered  off  and  washed.  This  insoluble  portion 
is  dissolved  in  dilute  hydrochloric  acid,  and  the  barium 
present  precipitated  with  sulphuric  acid  in  excess.  The 
barium  sulphate  is  filtered  out,  ignited,  weighed,  and  if 
this  weight  does  not  differ  materially  —  say  by  2  per 
cent,  —  from  the  weight  of  the  total  insoluble  matter, 
the  total  insoluble  matter  is  reported  as  barytes.  If  the 
difference  is  greater  than  this,  add  the  filtrate  from  the 
barium  sulphate  precipitate  to  the  water-soluble  portion 
of  fusion.  Evaporate  and  determine  the  silica  and  the 
alumina  in  the  regular  way.  Calculate  the  alumina  to 
China  clay  on  the  arbitrary  formula  2SiO>.  A12O3.  2H20, 
and  deduct  the  silica  in  it  from  the  total  silica,  reporting 
the  latter  in  a  free  state.  It  is  to  be  borne  in  mind  that 
China  clay  gives  a  loss  of  about  13  per  cent  on  ignition, 
\vhich  must  be  allowed  for.  China  clay  is  but  slightly 
used  in  white  paints  as  compared  with  barytes  and 
silica." 

"Sample  9  contains  sulphide  of  zinc. 


324  CHEMISTRY   AND   TECHNOLOGY  OF  PAINTS 

"  Samples  of  this  character  are  usually  mixtures  in 
varying  proportions  of  barium  sulphate,  sulphide  of  zinc, 
and  oxid  of  zinc.  Determine  barytes  as  matter  insolu- 
ble in  nitric  acid,  the  total  zinc  as  in  Case  i,  and  the  zinc 
soluble  in  acetic  acid,  which  is  oxid  of  zinc.  Calculate 
the  zinc  insoluble  in  acetic  acid  to  sulphide." 

"Sample  10  contains  sulphite  of  lead. 

"This  is  of  rare  occurrence.  Sulphite  of  lead  is  in- 
soluble in  ammonium  acetate,  and  may  be  filtered  out 
and  weighed  as  such.  It  is  apt  on  exposure  to  the  air  in 
the  moist  state  to  become  oxidized  to  sulphate  of  lead. 

"There  are  certain  positions  which  the  chemist  must 
take  in  reporting  analyses  of  white  paints: 

"First.  White  lead  is  not  uniformly  of  the  composition 
usually  given  as  theoretical  2PbC03  Pb(OH)2,  but  in 
reporting  we  must  accept  this  as  the  basis  of  calculating 
results,  unless  it  is  demonstrated  that  the  composition  of 
the  white  lead  is  very  abnormal. 

"Second.  In  reporting  oxid  of  lead  present  this 
should  not  be  done  except  in  the  presence  of  sulphate  of 
lead,  and  if  white  lead  is  present,  then  only  where  the 
oxid  is  more  than  i  per  cent;  otherwise  calculate  all 
the  lead  soluble  in  acetic  acid  to  white  lead. 

"  Third.  China  clay  is  to  be  calculated  to  the  arbi- 
trary formula  given. 

"In  outlining  the  above  methods  we  have  in  mind 
many  samples  that  we  have  analyzed,  and  the  combinations 
we  have  chosen  are  those  we  have  actually  found  present." 

ANALYSIS  OF  PAINTS 

Separation  of  Pigment  from  Vehicle. — The  can  of  paint 
is  weighed  off  and  if  free  from  water,  heated  on  the  steam 
bath  for  15  to  30  minutes.  Owing  to  the  marked  decrease 
in  the  specific  gravity  and  the  viscosity  of  the  paint 


ANALYSIS  OF  PAINT  MATERIALS  325 

vehicle  at  the  higher  temperature,  the  pigment  generally 
settles  to  the  bottom  very  quickly. 

In  the  case  of  paints  which  show  the  presence  of 
water,  it  is  best  to  allow  the  pigment  to  settle  out  in 
the  cold  in  order  to  avoid  any  saponifying  action  which 
the  pigment  might  exert  on  the  vehicle.  The  clear 
liquid  is  then  drawn  off  as  far  as  possible  and  set 
aside  for  analysis.  The  can  is  carefully  wiped  and 
weighed  again. 

About  25  g.  of  the  residue  in  the  can  are  weighed 
into  a  tall  weighing  tube.  A  mixture  of  benzol  and 
alcohol  i :  i  is  added  and  the  contents  carefully  stirred 
up  with  a  glass  rod.  Another  tube  containing  a  similar 
weighed  quantity  of  the  same  material  is  balanced  to 
within  o.i  of  a  gram  against  the  first  tube,  after  adding 
the  solvent  and  stirring. 

The  two  are  then  placed  in  the  opposite  receivers  of  a 
centrifuge  and  whirled  at  a  moderate  or  high  speed, 
(depending  upon  the  facility  with  which  the  pigment  set- 
tles out)  for  about  five  or  ten  minutes.  The  clear  liquid 
is  then  drawn  off.  the  tubes  balanced,  and  after  the 
addition  of  fresh  solvent,  stirred  and  again  centrifuged. 
This  is  continued  until  no  more  of  the  vehicle  can  be 
extracted. 

The  tubes  are  then  placed  in  an  air  oven  first  at  80° 
C.  and  then  at  100°  C.  until  dry.  From  the  weights  of 
the  tubes  before  and  after  extraction,  the  weight  of  paint 
extracted,  and  the  weights  of  the  can  with  and  without 
the  supernatant  liquid,  the  percentage  of  vehicle  and 
pigment  can  be  calculated. 

There  is  generally  left  with  the  extracted  pigment  a 
small  percentage  of  unextracted  matter  (probably  soaps 
resulting  from  the  interaction  of  pigment  and  vehicle, 
or  linoxyn),  for  which  allowance  must  be  made. 


326  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

The  extracted  pigment  is  analyzed  as  outlined  in  the 
chapter  on  "Methods  of  Analysis  of  Pigments." 

Determination  of  Volatile  Matter.1 — Weigh  off  into  a 
round  bottomed  flask,  50  to  75  g.  of  the  ready  mixed 
paint.  Connect  with  a  condenser  by  means  of  a  steam 
trap.  Pass  live  steam  through  until  no  more  of  the 
volatile  oil  comes  over.  Allow  the  distillate  to  separate 
from  the  water  and  analyze  separately.  Shut  off  the 
steam  and  drive  air  through  the  apparatus.  At  the  same 
time,  heat  the  contents  of  the  flask  to  130°  C.  The 
residue  is  analyzed  for  non-volatile  oils.  Acetone,  if 
present,  will  be-  found  in  the  aqueous  as  well  as  oily 
layers  of  the  distillate. 

Analysis  of  Non-volatile  Portion  Extracted  from  the 
Ready  Mixed  Paint,  as  Previously  Outlined. — As  a  rule, 
very  little  information  can  be  obtained,  in  the  present 
state  of  our  knowledge  of  this  subject,  from  the  analysis 
of  a  varnish  or  the  non- volatile  portions  of  a  paint  vehicle. 

Most  of  the  constants  or  characteristics  of  the  various 
ingredients  which  go  to  make  up  the  varnish  are  so  altered 
in  the  process  of  cooking  that  it  is  often  extremely  difficult, 
if  not  impossible,  to  distinguish  them  in  the  final  material. 

Rosin  can  generally  be  determined  qualitatively  and 
quite  often,  quantitatively,  but  even  here  it  is  some- 
times impossible  to  detect  it  in  admixture  with  other 
varnish  resins. 

DETERMINATION  OF  ROSIN 

(Twitchell  Method} 2 

Fatty  or  aliphatic  acids  are  converted  into  ethyl 
esters  when  acted  upon  by  hydrochloric  acid  gas  in  their 

1  Amer.   Soc.  Testing  Mat.  Report  of  Comm.  on  Preservative 
Coatings  for  Structural  Materials,  1903-1913. 

2  J.  Soc.  Chem.  Ind.  1891,  10,  804. 


ANALYSIS  OF  PAINT  MATERIALS  327 

alcoholic  solution;  rosin  acids  undergo  little  or  no  change, 
abietic  acid  separating  from  the  solution. 

Weigh  off  2  to  3  g.  of  the  mixed  fatty  or  rosin  acids 
in  a  flask,  dissolve  in  10  volumes  of  absolute  alcohol  and 
pass  a  current  of  dry,  hydrochloric  acid  gas  through  the 
solution,  the  flask  being  kept  cool  by  immersion  in  cold 
water.  After  about  45  minutes  the  reaction  is  complete, 
when  unabsorbed  HC1  gas  escapes. 

The  flask  is  allowed  to  stand  for  one  hour  to  permit 
complete  esterification  and  separation  of  the  ethyl  esters 
and  rosin  acids.  Dilute  the  contents  of  the  flask  with 
five  times  its  volume  of  water  and  boil  until  the  aqueous 
solution  has  become  clear. 

Gravimetric  Method.  —  Mix  the  contents  of  the  flask 
with  a  little  petroleum  ether  (b.p.  below  80°)  and  trans- 
fer to  a  separatory  funnel.  The  flask  is  washed  out  with 
the  same  solvent.  The  petroleum  ether  layer  should  be 
about  50  c.c.  in  volume. 

After  shaking,  the  acid  solution  is  removed,  the 
petroleum  ether  layer  washed  once  with  water,  then 
treated  in  the  same  funnel  with  45  c.c.  N/5  KOH  and  5 
c.c.  of  alcohol.  The  liquids  in  the  funnel  then  separate 
into:  i°  a  petroleum  ether  solution  floating  on  top,  and 
2°  an  aqueous  solution  containing  rosin  soap.  The 
soap  solution  is  run  off,  the  rosin  esters  liberated  by 
decomposition  with  dilute  hydrochloric  acid,  dissolved  in 
ether,  and  separated  by  evaporating  the  solvent  on  the 
steam  bath. 

Volumetric  Method. — The  acidified  mixture  is  poured 
into  a  separatory  funnel  and  the  flask  washed  a  few 
times  with  ether.  The  mixture  is  thoroughly  agitated, 
then  allowed  to  separate,  the  acid  layer  run  out,  and  the 
remaining  ethereal  solution  containing  the  mixed  ethyl 
esters  and  rosin  acids  washed  with  water  until  free  from 


328  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

hydrochloric  acid.  50  c.c  of  alcohol  is  then  added  and  the 
solution  titrated  with  standard  alkali,  using  phenolphthalein 
as  indicator.  The  rosin  acids  react  immediately,  forming 
rosin  soaps;  the  ethyl  esters  remain  unaffected. 

The  number  of  c.c.  of  N  alkali  is  multiplied  by  0.346, 
giving  the  amount  of  rosin  acids  in  the  sample. 

The  gravimetric  method  is  the  more  accurate  one,  due 
to  the  difference  in  combining  weights  of  the  rosin  acids 
in  different  samples  of  rosin.  The  results  obtained  by 
the  Twitchell  method  are  only  approximately  accurate. 

In  the  case  of  a  mixture  of  rosin  acids,  fatty  and  un- 
saponifiable,  saponify  with  alcoholic  KOH  and  drive 
off  the  alcohol  (after  dilution  with  water)  by  continued 
boiling.  Disregarding  the  undissolved  unsaponifiable, 
the  aqueous  soap  solution  is  transferred  to  a  separatory 
funnel  and  shaken  out  with  petroleum  ether;  this  removes 
the  unsaponifiable.  On  treating  with  mineral  acids,  the 
soap  solution  yields  a  mixture  of  rosin  and  fatty  acids 
which  are  separated  by  the  Twitchell  process. 

In  the  volumetric  method,  the  unsaponifiable  need 
not  be  separated  as  above.  2  g.  of  the  mixed  acids 
and  unsaponifiable  are  weighed  off  accurately,  titrated 
with  N  alkali  and  the  number  of  c.c.  (a)  noted.  Another 
2  g.  are  treated  with  HC1  gas  and  titrated  with  N  alkali, 
using  (b)  c.c.;  taking  346  as  the  combining  weight  for 
rosin  and  275  for  the  fatty  acids  (palmitic,  stearic  and 
oleic),  the  weight  of  the  rosin  acids  is  b  X  0.346;  the  weight 
of  fatty  acids  is  (a  —  b)  X  0.275,  and  the  weight  of  the  un- 
saponifiable equals  100  —  {b  Xo.346  +  (a  —  b)  X  0.275) . 

Separation  of  Rosin  Acids  from  Fatty. — After  the 
esterification  process,  we  get  a  mixture  of  free  acid  and 
esters,  and  after  titration  (e.g.  in  the  volumetric  process) 
we  get  a  mixture  of  rosin  soap  and  ethyl  esters  of  fatty 
acids.  If  the  alcohol  is  distilled  off  and  the  remaining 


ANALYSIS  OF  PAINT  MATERIALS  329 

mixture  treated  with  water,  the  soap  is  dissolved,  leaving 
the  esters  floating  on  top  of  the  soap  solution.  The 
two  layers  are  separated  and  the  soap  solution,  after 
washing  with  ether  to  remove  traces  of  esters,  yields 
rosin  acids  on  acidulating.  The  ethyl  esters  are  saponi- 
fied by  caustic  alkali  and  the  fatty  acids  separated. 

DETERMINATION  OF  ROSIN 

(Wolff  &  Scholze  Method]  l 

Quick  Titrimetric  Determination. —  2  to  5  g.  of  the 
rosin  —  fatty  —  acid  mixture,  according  to  the  quantity 
weighed  off,  are  dissolved  in  10  to  20  c.c.  of  absolute 
methyl  or  ethyl  alcohol,  treated  with  5  to  10  c.c.  of  a 
solution  of  one  part  of  sulphuric  acid  in  four  parts 
alcohol  (methyl  or  ethyl)  and  boiled  for  two  minutes 
with  reflux  condenser. 

The  reaction  liquid  is  then  treated  with  5  to  10  volumes 
of  7  to  10  per  cent  sodium  chloride  solution  and  the  fatty 
acid  esters  together  with  the  rosin  acids  extracted  with  ether 
or  a  mixture  of  ether  and  a  little  petroleum  ether.  The 
aqueous  solution  is  drawn  off  and  agitated  once  or  twice 
with  ether.  The  ethereal  solutions  are  united,  washed 
twice  with  dilute  sodium  chloride  solution  (or  when  the 
washed  water  is  not  neutral,  to  neutrality),  and  after 
the  addition  of  alcohol,  titrated  with  N/2  KOH. 

Assuming  an  average  of  160  as  the  acid  value  of  the 
rosin  acids  and  a  correction  for  unsaponifiable  fatty  acids 
of  1.5,  and  further  taking  "m"  as  the  amount  of  the 
weighed  fatty  —  acid  —  rosin  mixture  and  "a"  as  the 
number  of  c.c.  of  KOH  used  for  neutralization,  we  obtain 
as  the  rosin  acid  content  in  per  cent,  the  following: 

a.  17.  76 
~^T~       'I'S 
1  Chem.  Ztg.  38  (1914),  369,  382. 


330  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

The  amount  of  rosin  is  approximately  obtained  by 
multiplying  this  value  by  1.07. 

Gravimetric.  —  2  to  5  g.  of  the  fatty  acid  mixture 
are  treated  as  in  the  first  method.  After  neutraliza- 
tion, i  to  2  c.c.  more  of  alcoholic  KOH  are  added 
and  the  ethereal  solution  repeatedly  washed  with  water. 
The  wash  water  and  soap  solution  are  concentrated  to  a 
small  volume,  transferred  to  a  separatory  funnel,  acidi- 
fied, and  after  the  addition  of  the  same  amount  of  sodium 
chloride  solution,  extracted  two  to  three  times.  The 
ethereal  solution  is  dried  with  fused  sodium  sulphate  and 
the  ether  distilled  off  in  a  small  flask. 

The  residue  on  cooling  is  dissolved  in  10  c.c.  of 
absolute  ethyl  alcohol,  and  5  c.c.  of  a  mixture  of  i  part 
sulphuric  acid  with  0.4  parts  alcohol  are  added.  The 
mixture  is  allowed  to  stand  for  i^  to  2  hours  at 
room  temperature.  It  is  then  treated  with  7  to  10  volumes 
of  10  per  cent  sodium  chloride  solution,  extracted  with 
ether  two  to  three  times,  and  the  united  ether  extracts 
(after  twice  washing  with  dilute  sodium  chloride  and 
drying  with  fused  sodium  sulphate)  distilled  off. 

The  percentage  of  the  thus  isolated  rosin  acids  may  be 
multiplied  by  1.07  in  order  to  yield  approximately  the 
rosin  content. 

ROSIN  AND  ROSIN  OILS 

Liebermann-S torch  Reaction. — Dissolve  the  washed  and 
dried  mixed  acids  (obtained  by  saponification  of  the 
material  to  be  analyzed  and  liberating  the  acids  with 
dilute  hydrochloric  or  sulphuric  acid)  in  acetic  anhydride 
on  the  water  bath,  cool  and  add  a  few  drops  of  sulphuric 
acid  (specific  gravity  1.53). 

This  acid  is  made  by  mixing  34.7  c.c.  of  concentrated 
sulphuric  acid  with  35.7  c.c.  of  water,  yielding  62.53 


ANALYSIS  OF  PAINT  MATERIALS  331 

per  cent  sulphuric  acid.  The  presence  of  rosin  or  rosin 
oil  is  detected  by  a  very  fine  reddish  violet  coloration 
produced  on  the  addition  of  the  acid. 

Detection.  —  Rosin  oil  may  be  detected  by  the  Lie- 
bermann-Storch  reaction  already  mentioned,  or  by  the 
following : 1 

Stannic  bromide  is  prepared  by  adding  bromine  drop- 
wise  to  granulated  tin  in  a  dry  flask  immersed  in  cold 
water  until  an  excess  is  present.  Then  a  little  more 
bromine  is  added  and  the  whole  diluted  with  three  to 
four  volumes  of  carbon  disulphide.  The  reagent  thus 
obtained  is  stable. 

To  carry  out  the  test,  a  few  drops  of  the  rosin  oil  are 
placed  in  a  dry  test  tube  and  dissolved  in  i  c.c.  of  car- 
bon disulphide.  Add  the  stannic  bromide  reagent  grad- 
ually. If  rosin  oil  is  present,  the  liquid  assumes  an 
intense,  brilliant,  violet  coloration. 

It  may  be  necessary  to  dilute  with  more  carbon  disul- 
phide in  order  to  bring  out  this  color. 

On  standing,  a  violet  sediment  is  formed  in  the  tube 
from  which,  after  removing  the  liquid  and  warming  the 
residue  with  carbon  disulphide,  the  purple  coloration 
is  again  obtained  free  from  impurities. 

In  the  presence  of  much  mineral  oil,  mix  the  sample 
with  the  solution  of  stannic  bromide  in  carbon  disulphide, 
and  then  add,  drop  by  drop,  a  solution  of  bromine  and 
carbon  disulphide.  This  yields  the  coloration  unmasked 
by  any  due  to  the  mineral  oil. 

ROSIN  OIL 

Rosin  Spirit.  —  This  is  the  lighter  and  more  volatile 
portion  obtained  in  the  dry  distillation  of  rosin.     It  is 
separated  from  the  aqueous  acetic  acid  layer,  purified  with 
1  Allen,  "  Commercial  Organic  Analysis." 


332  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

sulphuric  acid  and  caustic  soda,  and  then  re-distilled. 
It  is  insoluble  in  water  or  alcohol,  but  soluble,  in  all  pro- 
portions, in  ether,  petroleum-ether  and  turpentine.  The 
specific  gravity  varies  from  0.856  to  0.883. 

Composition.  —  The  hydro-carbons,1  of  which  this  is 
principally  composed,  include  pentane  and  pentene  and 
their  homologues,  toluene  and  its  homologues,  tetra  and 
hexahydrotoluene  and  their  homologues,  terpenes,  etc. 
The  characteristic  constituent  of  rosin  spirit  is  hep- 
tine,  C7H12,  (methyl-propyl-allene) .  The  compound  boils 
at  103°  to  104°  C.,  and  has  a  specific  gravity  of  0.8031 
at  20°  C.  It  is  soluble  in  alcohol  and  ether,  absorbs 
oxygen  very  readily,  but  does  not  affect  ammoniacal 
cuprous  chloride  or  silver  nitrate. 

Rosin  Oil. — This  is  the  heavier  and  less  volatile  por- 
tion obtained  after  the  rosin  spirit  has  been  collected. 
It  generally  has  a  strong  fluorescence  although  the  lat- 
ter can  be  more  or  less  destroyed  by  hydrogen  peroxid, 
the  addition  of  nitro-benzol,  nitro-  or  dinitrotoluene, 
dinitronaphthalene,  or  by  heating  with  sulphur.  The 
specific  gravity  of  the  crude  rosin  oil  varies  from  0.96 
to  i.i  while  the  refined  generally  has  a  specific  gravity 
of  0.97  to  0.99. 

DETERMINATION  OF  WATER 

Qualitative.  —  Water  in  an  oil,  paint,  dryer  or  varnish 
may  be  detected  by  adding  a  few  c.c.  of  dry  mineral  oil 
to  an  equal  quantity  of  the  sample  in  a  test  tube  and 
shaking  vigorously  with  a  few  grains  of  a  strong  dye  like 
erythrosine,  rhodamine  or  methylene  blue.  Coloration 
proves  the  presence  of  water.  Solvents  like  alcohol, 
acetone  or  amyl  acetate  which  dissolve  these  dyes  must 
of  course  be  absent. 

1  Renard,  Amer.  Chem.  Phys.  1884  (6)  i,  323. 


ANALYSIS  OF  PAINT  MATERIALS  333 

The  presence  of  an  appreciable  quantity  of  water  in 
an  oil  is  indicated  by  the  crackling  produced  when  some 
of  it  is  heated  in  a  test  tube  beyond  212°  F. 

Quantitative. — -(i)  In  the  case  of  non- volatile  oils,  about 
5  g.  are  accurately  weighed  into  a  small  evaporating  dish 
or  watch-glass  and  dried  in  the  air  oven  at  100-110°  C. 
for  two  hours.  The  loss  in  weight  (except  where  volatile 
fatty  acids  are  present)  is  reported  as  moisture. 

For  accurate  determinations,  however,  the  above 
method  is  open  to  serious  objection.  In  the  case  of  soya 
bean  oil,  for  example,  owing  to  its  comparatively  high 
content  of  volatile  acids  and  glycerides,  the  results 
obtained  may  be  somewhat  high;  whereas  in  the  case  of 
linseed  oil  the  loss  due  to  moisture  may  be  more  than 
counter-balanced  by  the  gain  in  weight  due  to  oxidation. 

With  drying  oils,  the  following  method1  is  therefore 
recommended : 

(2)  A    small    Erlenmeyer    flask    fitted    with    a    cork 
through  which  pass  two  tubes,  a  long  tube  reaching  down 
to  the  bottom  of  the  flask  and  a  short  one  ending  just 
below  the  cork,  is  carefully  dried  and  weighed.     5  g.  of 
oil  are  then  introduced,  the  flask  placed  upon  a  steam 
bath,    and    dry    carbon    dioxid,    hydrogen    or    coal-gas 
passed  through  the  oil  for  i  or  2  hours  by  connecting  the 
short  tube  to  an  air  pump  or  aspirator.     The  flask  is  then 
carefully  dried  and  weighed. 

(3)  For    the   determination  of  water  in  oils  like  pine 
oil,    which    always    contain    an    appreciable    quantity    of 
water,   as  well   as  in   ready  mixed  paints,   the   method2 
outlined  on  the  next  page  is  very  useful: 

1  Determination  of  moisture  in  oils  in  a  current  of  air — Son- 
nenschein-Zeit.   anal.    Chem.    25,   373.    J.    Soc.    Chem.    Ind.    1886, 
508. 

2  Michel,  Chem.  Ztg.,  1913,  353. 


334  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

The  substance  containing  water  is  distilled  in  an  inert,  water- 
insoluble  medium,  lighter  than  water  and  having  a  higher  boiling 
point.  For  this  purpose  a  mixture  of  toluene  and  xylene  (1:2)  is 
found  most  suitable.  On  condensing  the  water  separates  quanti- 
tatively from  the  toluene-xylene  mixture. 

150  c.c.  of  a  dry  mixture  of  ^  pure  toluene  (b.  p.  110°  to  112°  C.) 
and  f  commercial,  pure  xylene  are  placed  in  a  300  c.c.  Jena  flask,  and 
the  substance  to  be  examined  added.  It  is  well  to  add  a  small  spiral 
of  aluminium  to  produce  uniform  ebullition.  The  distillate  is  col- 
lected in  a  separatory  funnel  about  10  cm.  in  diameter,  and  provided 
with  a  glass  cock  having  a  bore  of  at  least  5  mm.  A  10  c.c.  tube, 
graduated  in  o.i  or  0.05  c.c.,  in  which  the  water  is  collected  is  at- 
tached. The  distillate,  which  is  milky  in  appearance  on  account  of 
suspended  water,  is  best  separated  by  centrifuging.  The  amount  of 
water  is  then  read  off  on  the  graduated  tube.  The  toluene-xylene 
may  be  dried  over  calcium  chloride  and  used  again. 

(4)  Determination  of  water  by  means  of  calcium 
carbide  (see  U.  S.  Circular  No.  97,  of  the  Bureau  of 
Chemistry). 

ANALYSIS  OF  OILS 

Specific  Gravity. — This  is  determined  at  15.5°  C. 
(60°  F.).  For  most  technical  purposes  the  hydrometer 
is  universally  used.  Where,  however,  a  greater  degree  of 
accuracy  is  desired  or  where  the  amount  of  oil  available 
is  rather  small,  the  Westphal  or  Mohr's  balance,  the 
specific  gravity  bottle,  Sprengel's  picnometer  or  finally 
the  analytical  balance  may  be  used.  In  the  latter  case 
the  specific  gravity  is  determined  by  means  of  a  plummet 
suspended  from  one  of  the  balance  beams  and  immersed 
in  the  oil  maintained  at  15. 5°  C.  The  latter  is  contained 
in  a  beaker  or  short  cylinder  placed  upon  a  bridge  so  as 
not  to  interfere  with  the  balance  pans. 

If  the  plummet  weighs  in  air  a  grams,  in  water  w  grams,  and  in 
the  oil  at  15.5°  C.  o  grams, 


ANALYSIS  OF  PAINT  MATERIALS  335 

a  —  w  =  loss  in  weight  of  plummet  when  immersed  in  water 

=  weight  of  vol.  of  water  equal  to  vol.  of  plummet 
a  —  o   =  wt.  of  vol.  of  oil  equal  to  vol.  of  plummet 

a-  o  f    ., 

—  =  sp.  gr.  of  oil 

a  —  w 

For  the  determination  of  the  specific  gravity  of 
viscous  oils  Lewkowitsch  mentions  the  use  of  BruhPs 
picnometer. 

Eichhorn's  araeopicnometer  is  used  in  the  case  of 
very  small  quantities  of  oil. 

In  the  latter  case  also  the  specific  gravity  of  the  oil 
may  be  obtained  by  preparing  a  mixture  of  alcohol  and 
water  so  that  a  drop  of  the  oil  remains  in  suspension 
wherever  it  is  placed  in  the  mixture.  The  sp.  gr.  of  the 
alcohol-water  mixture  is  then  determined  by  means  of  a 
hydrometer. 

It  is  advisable  to  determine  the  specific  gravity  at 
15.5°  C.  Where,  however,  this  is  not  feasible  a  correc- 
tion1 must  be  made.  This  has  been  found  by  Allen  to 
be  approximately  the  same  for  most  vegetable  and  hydro- 
carbon oils,  and  is  equal  to  0.00064  for  i°  C.  or  0.00035 
for  i°  F. 

Saponification  Value. — This  expresses  the  number  of 
mgms.  of  potassium  hydroxid  necessary  to  completely 
saponify  the  glycerides  and  fatty  acids  in  i  g.  of  oil. 

Weigh  off  in  a  200  c.c.  Erlenmeyer  flask  about  2  g.  of 
oil,  add  25  c.c.  (from  a  pipette)  of  N/2  alcoholic  potash, 
and  heat  on  the  steam  bath  for  \  to  i  hour  with  reflux 
condenser.  The  contents  of  the  flask  should  boil  gently, 
and  should  be  agitated  occasionally.  When  saponification 
is  complete,  cool,  add.  5  drops  of  i  per  cent  phenolphthalein 
solution,  and  titrate  the  excess  of  alkali  with  N/2  hydro- 
chloric acid  solution.  A  blank  titration  is  made  with 

1  Allen,  Comm.  Org.  Anal.  1910,  Vol.  2,  pp.  49-51. 


336  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

25  c.c.  N/2  alcoholic  potash  which  has  been  heated  as 
outlined  above.  The  difference  between  the  two  titra- 
tions  shows  the  number  of  c.c.  of  N/2  HC1  equivalent 
to  the  KOH  required  to  saponify  the  oil. 

The  alcoholic  potash  must  be  prepared  from  pure  grain 
alcohol  (95  per  cent)  and  chemically  pure  caustic  potash. 
Dissolve  40  g.  of  the  stick  potash  in  about  25  c.c.  of 
water  and  dilute  with  alcohol  to  i  liter.  After  standing 
for  one  day  the  solution  may  be  filtered  from  the  precipi- 
tated potassium  carbonate  (which  the  stick  potash  always 
contains)  and  set  aside  in  a  uniformly  cool  place. 

The  saponification  value  of  an  oil  is  valuable  as  a  cri- 
terion of  its  freedom  from  adulteration  with  mineral  oils. 
It  does  not,  however,  assist  in  detecting  adulteration  with 
other  vegetable  oils,  since  most  of  the  naturally  occurring 
vegetable  oils  have  saponification  values  which  vary  be- 
tween rather  narrow  limits.  (See  table,  page  343.) 

Acid  Value. — This  expresses  the  number  of  mgms.  of 
potassium  hydroxid  necessary  to  neutralize  the  free 
fatty  acids  in  i  g.  of  oil. 

Weigh  off  5  to  15  g.  of  oil  in  an  Erlenmeyer  flask, 
add  50  c.c.  of  alcohol,  amyl  alcohol,  or  ether-alcohol 
mixture  (1:1),  add  2  to  3  drops  of  phenolphthalein  and 
titrate  against  N/io  or  N/5  caustic  potash  or  soda.  Of 
the  above  solvents  amyl  alcohol  and  ether-alcohol  dis- 
solve most  oils  and  resins  almost  completely.  They 
are  especially  valuable  in  the  case  of  viscous  oils.  Where 
alcohol  alone  is  used  it  is  generally  best  to  heat  it  with  the 
oil  for  a  short  time  on  the  steam  bath  before  titrating  in 
order  to  completely  extract  the  free  fatty  acids.  Titrate 
cold. 

In  the  case  of  resins,  and  especially  fossil  resins,  the 
method  must  be  modified  somewhat.  Dissolve  about  i  g. 
of  the  sample  in  50  c.c.  of  a  mixture  of  absolute  alcohol 


ANALYSIS  OF  PAINT  MATERIALS  337 

and  benzol  (i :  i)  or  a  similar  mixture  of  alcohol  and  ether 
by  boiling,  with  reflux  condenser,  on  the  steam  bath. 
Titrate  against  N/2  or  N/5  alcoholic  alkali.  It  has  been 
found  in  this  laboratory  that  aqueous  alkali  yields  acid 
values  much  higher  than  those  obtained  with  alcoholic 
alkali. 

Oils  which  have  been  thickened  by  blowing  generally 
have  a  lower  acid  value.  On  the  other  hand  we  have 
found  that  boiled  bodied  oils  show  a  fair  content  of  free 
fatty  acids. 

Same  Oil  Boiled 

Varnish  Oil  and  Bodied 

Sp.gr.  0.933  0.973 

Acid.  Val.         3.1  14 . 8 

Sapon.  Val.  194.2  IQ4-2 

Iodine  Val.    193 . 2  93 . 5 

Iodine  Value.  -  -  This  figure  represents  the  percentage 
of  iodine  chloride  (expressed  in  terms  of  iodine)  absorbed 
by  the  unsaturated  glycerides  and  acids  in  i  g.  of  oil. 

Hubl  Method.  —  About  0.15  g.  of  drying  oil,  0.25  g.  of 
semi-drying  oil  or  i  g.  of  non-drying  oil  is  weighed  off  in 
a  capsule,  placed  in  a  500  to  1,000  c.c.  glass-stoppered 
bottle,  and  dissolved  in  10  c.c.  of  chloroform  or  carbon 
tetrachloride.  25  c.c.  of  mercury  iodochloride  prepared 
as  shown  below  are  added  from  a  pipette.  Empty  the 
pipette  each  time  in  exactly  the  same  way,  draining  until 
one  or  two  drops  have  fallen.  Moisten  the  glass  stop- 
per with  potassium  iodide  solution,  and  set  the  bottle 
aside  in  the  dark.  If  after  two  hours  the  color  of  the 
solution  in  the  bottle  is  not  a  deep  brownish  red, 
add  another  25  c.c.  of  mercury  solution.  When  the 
reaction  is  complete  the  solution  should  contain  an  excess 
of  iodine  at  least  equal  to  the  amount  absorbed.  For 
semi-drying  oils  allow  8  hours  for  complete  absorption 


338  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

of  the  iodine;  for  drying  oils  allow  18  hours.  15  c.c. 
of  10  per  cent  potassium  iodide  solution  (or  more  in  case 
a  red  ppt.  of  mercuric  iodide  is  formed)  are  added, 
and  the  contents  of  the  flask  diluted  to  about  500  c.c.,  at 
the  same  time  washing  in  any  volatilized  iodine  trapped 
by  the  potassium  iodide  solution  on  the  stopper.  The 
excess  iodine  in  the  aqueous  and  chloroformic  layers  is 
titrated  against  N/io  sodium  thiosulphate  with  frequent 
agitation  until  the  color  of  both  layers  is  but  faintly 
yellow.  A  few  c.c.  of  freshly  prepared  starch  solution 
are  then  added,  and  the  titration  continued  until  the 
blue  color  is  discharged.  A  blank  containing  exactly 
the  same  quantities  of  solvent  and  mercury  iodochloride 
solution  must  be  set  aside  along  with  the  oil,  and  then 
titrated  after  the  addition  of  the  same  quantity  of  potas- 
sium iodide  and  water. 

The  difference  between  the  number  of  c.c.  of  sodium 
thiosulphate  required  to  neutralize  the  free  iodine  in  the 
blank  and  the  excess  iodine  with  the  oil  represents  the 
amount  of  iodine  absorbed  by  the  oil;  from  the  latter 
the  iodine  value  can  be  calculated. 

To  prepare  the  mercury  iodochloride  solution  (i) 
25  g.  of  pure  resublimed  iodine  are  dissolved  in  500  c.c. 
of  pure  alcohol;  (2)  30  g.  of  mercuric  chloride  are  dis- 
solved in  the  same  quantity  of  alcohol  in  another  bottle. 
On  mixing  the  above  two  solutions  and  allowing  to  stand 
for  12  to  24  hours  a  solution  of  mercury  iodochloride  is 
formed  containing  i  molecule  of  iodine  (I2)  to  one  mole- 
cule of  HgCL..  The  mixed  solution  cannot  be  used  for 
making  iodine  value  determinations  when  it  is  older  than 
24  hours.  However,  the  two  solutions  in  themselves 
will  keep  indefinitely.  It  is  therefore  best  to  prepare 
only  as  much  iodochloride  solution  as  is  required. 

The   sodium   thiosulphate   solution   is   made   by   dis- 


ANALYSIS  OF  PAINT  MATERIALS  339 

solving  25  g.  of  the  crystals  in  1,000  c.c.  of  water.     It 
may  be  standardized  by  either  of  the  following  methods: 

(a)   Against  Potassium  Permanganate 

Dissolve  i  or  2  g.  of  pure  potassium  iodide  in  a  400 
c.c.  flask,  using  a  small  amount  of  water;  add  5  c.c.  of 
hydrochloric  acid  (1:1)  and  then  20  or  25  c.c.  of  an 
accurately  standardized  N/io  potassium  permanganate 
solution;  the  liberated  iodine  is  titrated  with  the  sodium 
thiosulphate  solution  after  diluting  to  200  c.c.  The 
reaction  involved  is  indicated  below: 

2KMnO4+  ioKI+  i6HCl=  I2KC1+  2MnCl2+  8H20+  id. 

(b)  Against  Potassium  Bichromate 
K2Cr2O7+  6KI+i4HCl  =  8KC1+  2CrCl3+  7H20+  61 


Weigh  off  accurately  3.8633  g.  of  pure  potassium 
dichromate  and  dissolve  in  exactly  1,000  c.c.  of  \vater. 
This  quantity  of  dichromate  solution  is  equivalent  to 
exactly  10  g.  of  iodine  liberated  according  to  the  above 
equation.  In  a  600  c.c.  Erlenmeyer  flask  place  10  c.c. 
of  10  per  cent  potassium  iodide  solution  and  5  c.c.  of 
hydrochloric  acid  (1:1),  and  add  exactly  20  c.c.  of  the 
dichromate  solution  from  a  burette.  Dilute  to  300-400 
c.c.  and  titrate  against  sodium  thiosulphate  after  adding 
starch  solution.  The  end  point  is  indicated  by  a  change 
in  the  color  of  the  solution  from  deep  blue  to  pale  green. 

The  starch  solution  is  best  prepared,  as  needed,  by 
shaking  up  about  0.5  g.  starch  with  50  c.c.  of  water, 
heating,  and  boiling  for  i  or  2  minutes.  The  solution 
should  be  cooled  before  being  used.  The  dichromate 
solution  keeps  indefinitely  and  may  be  used  for  stand- 
ardizing the  thiosulphate  solution,  the  strength  of  which 
varies  slightly  with  age. 


340  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

Wijs  Method.  —  Dissolve  13  g.  of  iodine  in  glacial 
acetic  acid,  and  determine  accurately  the  amount  of 
iodine  present,  using  25  c.c.  for  the  determination.  Then 
pass  dry  chlorine  gas  into  the  solution  until  the  color 
changes  suddenly  from  deep  reddish  brown  to  pale  yellow, 
due  to  the  complete  transformation  of  the  iodine  into 
iodine  chloride.  The  iodine  equivalent  of  this  solution 
must  be  exactly  twice  that  of  the  original  iodine  solution. 
If  a  titration  shows  more  than  double  the  iodine  equiva- 
lent, there  is  an  excess  of  chlorine  and  enough  iodine 
should  be  added  to  combine  with  it.  If  the  analysis 
shows  less  than  double  the  amount  of  iodine  there  is  still 
an  excess  of  iodine  and  more  chlorine  should  be  added. 

The  iodine  value  determination  is  carried  out  exactly 
as  in  the  case  of  the  Hiibl  method;  the  time  of  absorp- 
tion, however,  is  very  much  less,  being  \  hour  for  non- 
drying  oils,  i  hour  for  semi-drying  oils,  and  2  to  6  hours 
for  drying  oils  and  marine  animal  oils. 

According  to  Allen,  absorption  in  the  case  of  oils  of 
low  iodine  value  is  complete  in  4  minutes,  while  those 
of  higher  value  require  not  more  than  10  minutes,  provided 
too  much  oil  is  not  taken.  In  this  laboratory  we  have 
made  it  a  practice  to  allow  about  i  hour  for  semi-drying 
and  drying  oils. 

The  values  obtained  by  the  Wijs  method  are  as 
accurate  as  those  obtained  by  the  Hiibl  method,  and  agree 
very  closely  with  the  latter. 

BROMIDE  TEST 

It  has  been  found l  that  on  treating  the  ethereal 
solutions  of  certain  oils  with  a  slight  excess  of  bromine, 
an  insoluble  precipitate  is  obtained. 

1  Hehner  &  Mitchell,  Analyst,  1898,   23,  313. 


ANALYSIS  OF  PAINT  MATERIALS  341 

Method.  —  Dissolve  i  or  2  g.  of  oil  in  40  c.c.  of 
ether,  add  a  few  c.c.  of  glacial  acetic  acid  (the  precipi- 
tate formed  with  bromine  is  more  granular  when  the  acid 
is  used),  stopper  the  flask,  and  cool  to  5°  C.  Add 
bromine,  drop  by  drop,  from  a  very  fine  pipette  until  the 
brown  coloration  persists.  The  temperature  must  not 
be  allowed  to  rise. 

Allow  to  stand  for  3  hours  at  5°  C.,  filter  (preferably 
by  suction),  and  wash  four  times  with  ice-cold  ether. 
The  residue  is  dried  in  the  water  oven  and  weighed. 

The  insoluble  bromides  obtained  from  linseed  oil  melt 
at  140  to  145°  C.  and  contain  about  56  per  cent  bromine. 
Those  obtained  from  marine  animal  oils  decompose  be- 
fore melting.  This  property,  therefore,  furnishes  a  good 
method  of  detecting  small  amounts  of  the  latter  in 
linseed  oil. 

The  bromide  test  is  useful  in  the  examination  of 
boiled  and  bodied  oils.  Lewkowitsch l  has  found  that 
the  process  of  boiling  linseed  oil  decreases  the  yield  of 
insoluble  bromides. 

On  the  other  hand,  an  oil  which  has  been  bodied  by 
blowing  at  a  low  temperature  will  give  as  high  a  yield 
of  bromides  as  the  oil  from  which  it  is  prepared. 

Lewkowitsch  recommends  that  the  mixed  fatty  acids, 
carefully  prepared  in  an  atmosphere  of  carbon  dioxid 
or  hydrogen,  be  used  in  making  the  bromide  test.  The 
precipitate  then  obtained  is  much  easier  to  filter  than 
when  the  oil  is  used. 

According  to  Eibner  and  Muggenthaler,2  the  bromide 
test  is  carried  out  as  follows: 

2  g.  of  the  mixed  fatty  acids  are  dissolved  in  20  c.c. 
of  dry  ether,  and  cooled  to  minus  10°  C.;  0.5  c.c. 

1  Farben  Ztg.,  1912,  33  ff. 

2  Muggenthaler,  Inaug.  Dissert.,  1912,  Augsburg. 


342  CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 

of  bromine  are  added,  drop  by  drop,  from  a  very  fine 
pipette,  allowing  about  20  minutes  for  the  addition  of 
this  amount  of  bromine.  Another  0.5  c.c.  of  bromine 
are  then  added  in  10  minutes'  time.  The  temperature 
must  not  go  beyond  —  5°  C.  The  flask  is  corked  and  set 
aside  for  2  hours  at  —  10°  C.  The  solution  is  then  filtered 
through  a  weighed  asbestos  filter,  and  washed  5  times 
with  dry  ice  cold  ether,  using  5  c.c.  each  time. 

The  precipitate  is  then  dried  for  2  hours  at  80  to  85° 
and  cooled  in  a  dessicator. 

HEXABROMIDES  BY  THE  ABOVE  METHOD 

Fatty  Acids  from  Per  Cent 

PerillaOil 64.12 

Linseed  Oil  (Baltic) 57-96 

Linseed  Oil  (Dutch) 51 . 73 

Linseed  Oil  (La  Plata) 51 . 66 

Linseed  Oil  (Indian) 50 .50 

Tung  Oil nil 

Soya  Bean  Oil up  to       .78 

Poppy  Seed  Oil nil 

The  melting  point  of  the  bromides  obtained  by  Eibner 
and  Muggenthaler  from  the  mixed  fatty  acids  of  linseed 
oil  was  177°  C. 

The  following  table  will  give  an  idea  of  the  yield  of 
bromides  obtained  from  various  oils: 

Material  Per  Cent 1 

Perilla  Oil 53.6 

Linseed  (iodine  value  181.) 23 . 14  :  23 . 52 

Linseed  Oil  (iodine  value  186.4) 24. 17 

Linseed  Oil  (iodine  value  190.4) 37. 72 

Tung  Oil nil 

Hempseed  Oil 8.82 

Walnut  Oil 1.42:1.9 

Soya  Bean  Oil 3 . 73 

Poppy  Seed  Oil nil 

1  Lewkowitsch,  Vol.  I,  p.  477. 


ANALYSIS  OF  PAINT  MATERIALS  343 

Material  Per  Cent 

Soya  Bean  Oil 3 . 62 

Corn  Oil nil 

Cottonseed  Oil 

Menhaden  Oil 61.8 

Cod  Oil    32.68:  30.62 

Seal  Oil 27.54  :  27.92 

Whale  Oil 15 . 54  :  25 . 

SOME  CHARACTERISTICS  AND  VARIABLES  OF  COMMERCIAL  BOILED  OILS 


Description 

Specific 
gravity 
at  15.5°  C 

Acid 
value 

Saponifi- 
cation 
value 

Iodine 
value 

Somewhat  thin  and  fluid  

13.4 

Per  cent 
101  .  3 

Very  viscid                           

24.9 

77.  3 

Tacky  yielding  strings  

32  .6 

73.  7 

188  1-192 

I4s  .  I—  I<C7  .  2 

140.  7—1  s3  .4 

Very  thin 

O  047 

8.8, 

182  2 

Thin 

O  04.8 

7  06 

180  9 

Thin 

o  061 

12    43 

170    => 

Stout                

0.972 

19.69 

189.3 

Stout                    

0.082 

20.89 

18=;.  6 

Very  stout                

0.083 

24.97 

183.0 

Solid                               

I4.O2 

I(H  -0 

Varying    in    consistence    in    the 
same  order,  from  thin  to  very 
viscous  

4.8 

5-2 

7-8 
9-5 

9-  ! 

188.7 
189.1 
189.1 

1  86.  6 

187.2 

159-0 
100.7 

95-6 
83.6 
79-  x 

Double  boiled  oil,  I  

o  .  9493 

11.7 
18.8 

187.2 
192.3 
191  .0 

76.2 
71.1 
161  .0 

"       "    II 

o  o^o^ 

o  98 

102    3 

"           "       "    III 

o  9621 

3  °° 

192  8 

Commercial  boiled  oils,  8  samples.  . 

0-9355- 
0.9474 

2.8-6.4 

187.5- 
192.2 

180.4-183.3 

CHARACTERISTICS  OF  BOILED  OILS  (LEWKOWITSCH) 


Name 

Specific  gravity 

Iodine  value 

Ether-insoluble 
bromides  from 
glycerides 

Linseed  oil  (raw)             

0.0308 

186.4 

Per  cent 
24.17 

Pale  boiled  linseed  oil  
Double  "          "        "  

Ozonised          "        "  

«                 «        it 

n                 a        « 

0.9429 

0-9449 
0.9310 
0.9388 
0.9483 

171  .0 
169.96 
180.1 
171.2 
169.7 

20.97 

13-03 
36.26-36.34 

25-73 
30.19 

344 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


THE  CONVERSION  OF  FRENCH  (METRIC)  INTO  ENGLISH  MEASURE 


i  cubic  centimeter   = 

17  minims. 

2  cubic  centimeters  = 

34 

u 

3 

51 

u 

4 

68 

"       or  i  dram 

8  minims. 

5 

85 

u 

i      " 

25 

6               " 

IOI 

" 

i      " 

7 

118 

u 

i      " 

58 

8 

135 

It 

2  drams 

IS 

9 

152 

2         " 

32 

10 

169 

" 

2         " 

49 

20                       " 

338 

" 

5      " 

38 

30 

i 

507 

I 

i  ounce 

o  dram    27  minims. 

40 

I 

676 

' 

i      " 

3  drams  16 

50 

t 

845 

' 

i      " 

6       ' 

5 

60 

I 

1014 

' 

2  ounces 

0         ' 

54 

70 

'              = 

1183 

I 

2         " 

3       ' 

43 

80 

= 

*352 

I 

2         " 

6       ' 

32 

90 

= 

1521 

" 

3      " 

i       ' 

21 

IOO 

'                  = 

1690 

" 

3      " 

4        ' 

IO 

IOOO                         '                        = 

i  liter  = 

34  fluid  ounces  nearly,  or  2^  pints. 

. 

THE  CONVERSION  OF  FRENCH  (METRIC)  INTO  ENGLISH  WEIGHT 

The  following  table,  which  contains  no  error  greater  than   one-tenth   of  a 
grain,  will  suffice  for  most  practical  purposes: 


1  gram   = 

2  grams  = 
3 

4 
5 
6 

7 


9 

10 
ii 

12 
13 
14 
15 

16 

17 

18 
19 

20 
30 
40 

5° 

60 
70 
80 
90 

IOO 

IOOO 


grains. 


39* 


=  92I 

=  108 

=  I23f 

=  154? 

=  169* 

=  185* 

=  200- 

=  216 

=  247J 


=    293^ 

=    463 
=    617! 
=    774 
=    926 
=  1080! 

=   J234f 

=  1389 


dram 


i*  grain. 
7!  grains. 


1  48 

2  drams    3f 

18* 
34* 
49* 

Si 

20f 
36 

5i* 

7 


2 
2 
2 
3 
3 
3 
3 
4 
4 
4 
4 
5 
7 
10 

12 
IS 

18 

20 
23 

25 


=  i  kilogram  =  32  oz.,  i  dr.,  i2§  gr. 


37 


43 


26 

of 
34f 

9 
43* 


ANALYSIS  OF  PAINT  MATERIALS 


345 


METRIC  SYSTEM  OF  WEIGHTS  AND  MEASURES 
Measures  of  Length 


Denominations  and  Values 

Equivalents  in  Use 

10,000  meters. 
1,000  meters. 
100  meters. 
10  meters, 
i  meter, 
i-ioth  of  a  meter, 
i-iooth  of  a  meter, 
i-ioooth  of  a  meter. 

6.2137  miles. 
.62137  mile,  or  3,280  ft.  10  ins. 
328.            feet  and  i  inch. 
393  .  7           inches. 
39.37        inches. 
3.937      inches. 
•  3937    inch. 
.  0394    inch. 

Meter 

Measures  of  Surface 


Denominations  and  Values 


Equivalents  in  Use 


Hectare  

10,000  square  meters. 

2.471  acres. 

Are         

100  square  meters. 

Measures  of  Volume 


Denominations  and  Values 


Names 

No.  of 
Liters 

Cubic  Measures 

Dry  Measure 

Wine  Measure 

Kiloliter  or  stere. 
Hectoliter  
Dekaliter  
Liter  

1,000 

IOO 

10 

i 

i  cubic  meter, 
i-ioth  cubic  meter. 
10  cubic  decimeters, 
i  cubic  decimeter. 

i  .  308    cubic  yards. 
2            bu.  and  3.35  pecks. 
9  .  08      quarts. 
.  908    quart. 

264  .  1  7     gallons. 
26.417  gallons. 
2.6417  gallons. 

Deciliter  
Centiliter 

I-IO 

i-ioth  cubic  decimeter. 

6.  1023  cubic  inches. 

.845     Kill- 

Milliliter 

i  cubic  centimeter 

> 

Equivalents  in  Use 


Weights 


Denominations  and  Values 

Equivalents 
in  Use 

Names 

Number  of 
Grams 

Weight  of  Volume  of  Water 
at  its  Maximum  Density 

Avoirdupois 
Weight 

1,000,000 
100,000 
10,000 
1,000 

IOO 

10 

i 

I-IO 
I-IOO 
I-IOOO 

i  cubic  meter, 
i  hectoliter. 
10  liters, 
i  liter, 
i  deciliter. 
10  cubic  centimeters, 
i  cubic  centimeter, 
i-ioth  of  a  cubic  centimeter. 
10  cubic  millimeters, 
i  cubic  millimeter. 

2204.6        pounds. 
220.46      pounds. 
22.046    pounds. 
2  .  2046  pounds. 
3.5274  ounces. 
•  3527  ounce. 
iS-432    grains. 
1-5432  grains. 
•1543  grain. 
.0154  grain. 

Quintal                    

Hectogram  

Centigram  

For  measuring  surf  aces,  the  square  dekameter  is  used  under  the  term  of  ARE;  the  hectare,  or  100 
ares,  is  equal  to  about  2$  acres.  The  unit  of  capacity  is  the  cubic  decimeter  or  LITER,  and  the  series 
of  measures  is  formed  in  the  same  way  as  in  the  case  of  the  table  of  lengths.  The  cubic  meter  is  the 
unit  of  measure  for  solid  bodies,  and  is  termed  STERE.  The  unit  of  weight  is  the  GRAM,  which  is 
the  weight  of  one  cubic  centimeter  of  pure  water  weighed  in  a  vacuum  at  the  temperature  of  4  deg. 
Cent,  or  39.2  deg.  Fahr.,  which  is  about  its  temperature  of  maximum  density.  In  practice,  the  term 
cubic  centimeter,  abbreviated  c.c.,  is  generally  used  instead  of  milliliter,  and  cubic  meter  instead  of 
kiloliter. 


346 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


SPECIFIC  GRAVITY  OF  VARIOUS  MATERIALS 


Acetic  Acid 

Acetone 

Acetylene 

Acrylic  Acid 

Agate 

Alabaster 

Aluminium  Oxid 

"          Sulphate 

"    i8H2O 

Alum,  Potassium 

"      Soda 

"      Ammon.  Chrome. . 
"      Potass.  Chrome.  .  . 

Amber 

Ammonia  (gas) 

(liq.) 

Ammonium  Carbonate 

NH4HCO3.. 

Chloride 

"  Nitrate 

Sulphate 

"  "       acid 

Amyl  Acetate 

"     Alcohol 

"     Valerianate 

Aniline 

Anthracene 

Anthracite 

Antimony  Oxid,  Tri 

"      Tetra  .  . 

"      Penta.. 

Pentasulphide . 

Arsenic  Bisulphide 

"       Pentoxid 

Trioxid 

Asbestos 

Asphalt 


1.0607  V 
.788-.  790 
.92 

1.0621  *£ 

2.5-2.8 

2.3-2.8 

3-75-3-99 

2.71 

1.62 

i-75 

1.65 

1.719 

1.81278  (o.°) 

i.o-i.i 

•5971 

-6234  (o.°) 

1.586 

1.520  (17. ) 
1-725  (15- ) 

1.7687  y 
1.787 

.8792  (20.°) 

.8I44-.8330 
.8812  (o.°) 

1.0276  (l2.°) 

I.I47 

I.4-I.7 

5-2-5-7 
4.07 
3.78 
4.120  (o.  ) 

3-4-3-6 

3.99-4.25 

3.646 

1.2 

I. I-I.5 


Barium  Carbonate 4.27-4.37 

Chloride  2H2O... 3.097  2?4 

"       Peroxid 4.958 

"        Sulphide 4.25 

"        Sulphate 4.33-4.476 

Barley 5I--69 

Barytes 4.476 

Basalt 2.7-3.2 

Bees  Wax  (see  wax). 
Beefsuet  m.p.  3i.°-3i.5° 

C 968 

Bellmetal 8.81 

Benzene  b.p.  80.5°  C 8799(2o.°C.) 

Benzoic  Acid 1.201  (21.°) 

Blanc  Fixe 4.02-4.53 

Blue  Vitriol 2.27 

Bones 1.7-2.0 

Boric  Acid 1.46 

Butter 86S-.868 

Butyric  Acid 9599  ^ 


admium  Sulphide  (artif.) .  .  .3.9-4.8  C 
"  (Greenockite)  .4.8-4.9 

Calcium  Carbide 2.22 

Carbonate 2.72-2.95 

Chloride  (6H2O)i.654 

"      2.26 

Fluoride 3.15-3.18 

Hydroxid 2.078 

Oxid 3.15-3.40 

Sulphate 2.964 

(Gypsum) 2.32 

Sulphide 2.8 

Tungstate 6.062 

Camphor 992 

Caoutchouc 92-.96 

Carbolic  Acid 1.0597  (33.°) 

Carbon  (Amorphous).  . .  .1.75-2.10 

(Graphite) 2.10-2.585 

(Diamond) 3-47-3-5585 

Dioxid J-529 

Bisulphide 1.28 

Monoxid 0.967 

Tetrachloride . ...  1.59 

Cast  Iron 7.25 

Cellulose 1.27-1.45 

Charcoal  (Airfilled) 0.4 

"         (Airfree) 1.4-1.5 

Chlorine 2.491 

Chloroform 1-5264 

Chrome   Alum    Cr2(SO4)3. 

K2SO4.  24H2O 1.81278 

Chromic  Oxid 5.04 

Chromium 6.92 

Chromium  Trioxid 2.67-2.82 

Citric  Acid 1.542 

Clay 3.85 

Cobalt  Chloride 2.94 

Cobaltic  Oxid  (Co-A)  ..  .4.81-5.6 
Cocoabutter  (m.  p.  33.5°- 

34-°C) 89-.9i 

Copal 1.04-1.14 

Copper 8.91-8.96 

Copper  Carbonate,  Basic. 3. 7-4.0 

Cork 24 

Corundum 4.0 

Cotton  (Airdry) 1.47-1.5 

Cryolite  AlF33NaF 2.9 

Cupric  Hydroxid 3.368 

"       Oxid  (Black) 6.32-6.43 

"       Sulphate 3-5i6 

"       Sulphate  (sH2O)..  2. 284 

"       Sulphide 3.8-4.16 

Cuprous  Oxid  (Red) 5.75-6.09 

Cymene  b.  p.  i75.°-i76.°  0.862  (20.°) 

Bextrin 1.0384 

Biamond 3-49-3-52 

Bolomite 2.9 


ANALYSIS  OF  PAINT  MATEIRALS 


347 


SPECIFIC  GRA VITY  OF  VARIOUS  MATERIALS  —  Continued 


Earth: 

Gravel,  dry 1.4 

Humus 1.3-1.8 

Lean 1.34 

Loam i  .6— i  .9 

Ethane 1.036 

Ether  (Diethyl) 0.7183  (17.°) 

Ethyl  Acetate 892O-.QO28 

Ethyl  Alcohol 7937  ]?5 

Ethylene 9784 

Eucalyptol.  .    9267  (20.°) 

Eugenol 0630  (18.°) 

Ferric  Chloride 2.804  (IO-8  ) 

Hydroxid 3-4-3-9 

"      Oxid 5.12-5.24 

Ferrous  Carbonate 3.70-3.87 

"        Sulphate 1.86-1.90 

"        Sulphide 4.75-5.04 

Flax  (airdry) 1.5 

Fish  Oil 0.920-0.928 

Formaldehyde  (-20.°) 8153 

Formic  Acid 1.219-25° 

"    1.244-0° 

Fumaric  Acid 1.625 

Furfural 1.1594  -•£ 

Gasoline  (b.  p.  7o°.-9o.°) .  .66-.6g 

Gas  Carbon i .  88 

Glass: 

Window 2.4-2.6 

Mirror 2.45-2.72 

Crystal 2.95 

Flint 3-0-5-9 

Glue 1.27 

Gneiss 2.4-2.7 

Granite 2.51-3.05 

Graphite  (Natural) 2.17-2.32 

"         (Artificial) 2.10-2.25 

Gum  Arabic 1.31-1.45 

Guttapercha 981 

Gypsum 2.32 

Hemp  (Air-dry) 1.5 

Hornblende 3.0 

Hydriodic  Acid 4-3737A 

Hydrobromic  Acid I.278A 

Hydrochloric  Acid i-iQS  (8°) 

Hydrocyanic  Acid 697  (18.°) 

Hydrofluoric  Acid 9879  (15.°) 

Hydrogen 06949 

Hydrogen-peroxid 1-4584  (o.°) 

Hydrogen-sulphide 9-1.1895 

Hydroquinone 1.326 

India  Rubber 93 

Indigo 1.35 

lodic  Acid 4.629  (o.°) 


Iodine 4.948  (17.°) 

lodoform 4.09 

Iron  (pure) 7.85-7.88 

(gray  pig) 7-O3~7-i3 

(white  pig) 7-58-7-73 

(cast) 7-217 

(wrought) 7.86 

Bisulphide 4.86-5.18 

'     Sesquioxid 5.12 

Ivory 1.82-1.92 

Japan  QWax  (m.  p.  53.5°- 
54-5°) 992 

Kaolin. .  . .  2.2 


Lactic  Acid 1.2485 

Lard  (m.  p.  41.5-42.0.)-  •   -92-.94 

Lava 2.00-3.00 

Lead  (milled  sheet) 11.42 

(wire) 11.28 

Acetate.  3H2O 2.50 

Carbonate 6.43 

,  Basic. .  .6.323—6.492 

Chloride 5.8 

Chromate 6.123  (X5-0) 

Hydroxid 

(3PbOH20) 7-592 

Iodide 6.12 

Nitrate 4.5 

Oxid  (PbO) 9-2-9.5 

"      (Pb304) 9-096  (i5-°)C 

Sulphate 6.23 

Sulphocyanate 3,82 

Tungstate 8.235 

Leather 86-1.02 

Lime  (unslacked) 1.3-1.4 

"      (slacked) 2.3-3.2 

Limestone 1.86-2.84 

Linoleum 1.15-1.3 

Linseed  Oil  (raw) 93  -.934 

"    (boiled) 934--94Q 

Litharge  (natural) 7.83-7.98 

"        (artificial) 9.3-9.4 

Lithium  Carbonate 2.111 

"        Chloride 1.998-2.074 

Malachite 3.85 

Manganese  Chloride 

(MnCl2.4H2O) 1.913 

Manganese  Nitrate 1.82 

Oxid  (MnO).. 5.09-5.18 
"      (MnO2)5.026 
"     (Mn2O3)4-325-4-82 
Sulphate 

(MnSO47H2O) . .  2.092 
Marble : 

African 2.8 

British 2.71 


348 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


SPECIFIC  GRAVITY  OF  VARIOUS  MATERIALS  —  Continued 


Marble: 

Carrara  ..............  2.72 

Egyptian,  Green  ......  2.67 

Florentine  ............  2.52 

French  ...............  2.65 

Marl  ..................  1.6-2.5 

Masonry  : 

Ashlar  Granite  ........  2.37 

"       Limestone  .....  2.32-2.70 

"       Millstone  ......  2.01-2.51 

"       Sandstone  ......  2.61 

Rubble  (dry)  .........  2.21 

"        (mortar)  ......  2.42 

Meerschaum  .............  99-1.28 

Mercuric  Chloride  .......  5.32-5.46 

"         Oxid  ..........  11.0-11.29 

Mercuric  Sulphide: 

(HgS  black)  ..........  7-55-7-70 

(HgSred)  ............  8.06-8.12 

Mercurous  Chloride: 

(Calomel)  ............  6.482-7.18 

Methyl  Alcohol  ..........  7984  (15.°) 

Methyl  Ethyl  Ether  ......  7252  (o.°) 

Mica  ..................  2.65-3.2 

Milk  (cow's)  ............  1.028-1.035 

Milk  Sugar  .............  1-525  (20.°) 

Molybdic  Acid: 

H2MoO4H2O  ..........  3.124  (15°) 

Morphine  ..............  1.317-1.326 

Mortar  (hardened)  ......  1.65 

Mutton  Suet  (m.p.47.°  C.)  .92 

Napthalene  ............. 


C.) 
Naphthol  a  .............  1.224  (4-°  C.) 

"         £  ............  1.217(4-°  C.) 

Neatsfoot  Oil  ............  914  (39.  F.) 

Nickel  (rolled)  ..........  8.67 

(cast)  ...........  8.28 

Nicotine  ...............  i.on  2?° 

Nitraniline  m  ...........  1.43 

P  .............  1-424 

Oats  ....................  43 

Ochre  .................  3.50 

Oleic  Acid  ...............  8908 

(1-2.°  C.) 

Oolitic  Stones  ...........  1.89-2.6 

Opal  ...................  2.  20 

Oxalic  Acid  .............  1.653  (i8.°C.) 

Ozone  .................  1.658  (A.) 

Palmitic  Acid  ............  8465 

(7-6°  C.) 

Palm  Oil  (m.  p.  3O.°C.)  .  .  .   .905 

Paper  ...................  70-1.15 

Paraffine: 

m.  p.  38.-52.°C  ........  87-.8S 

m.  p.  52.-s6.°C  .........  88-93 


Pearls 2.72 

Peat 1.2-1.5 

Petroleum  Ether: 

b.  p.  4<D.-7o.°C 6s-.66 

Phenol    1.0597  (33-°C.) 

Phosphorus  (yellow) 1.8232 

(red) 2. 1 1 

Phthalic  Acid 1.585-1.593 

"    anhydride...  1.52 7  (4.°  C.) 

Picric  Acid 1.813 

Pinene 8587 

(20.°  C.) 

Pitch 1.07-1.10 

Plaster  of  Paris 2.96 

Platinum 21.52 

Porcelain : 

Berlin 2.29 

Meissen 2.49 

Sevres 2.24 

China 2.38 

Portland  Cement 1.25-1.51 

Potash 2.10 

Potassium 875  (13°) 

Bromide 2.756  2^ 

Carbonate.  .  .  .2.29 
"    (2H2O)  2.043 

Chlorate 2.344  (17.°) 

Chloride i  .994  ^ 

Chromate.  ...  2.721  (4°) 

Cyanide 1.52  (16  ) 

Bichromate.  .  .2.692  (4°) 
Ferricyanide.  .1.8109  (17°) 
Ferrocyanide  .  1.8533  (*/ ) 

Hydroxid 2.044 

Iodide 3.043  (24.3°) 

Nitrate 2.1  (4.°) 

Permanganate  2.70 

Sulphate 2.6633  ¥ 

"      ,  Acid  2.245 
Sulphide  K2S. .  2.13 
Sulphocyanate  1.906 

Tartrate 1-975 

Potatoes i.io 

Pumice   nat.) 37--9° 

"        (artif.) 2.2-2.5 

Pyridin 9855  (15  °) 

Pyrogallol 1-463  (40.°) 

Realgar  As2S2 3-4-3-6 

Red  Lead 9.07 

Rosin 1.07 

Ruby 3.95-4.02 

Salt  (table) 2.15-2.17 

Sand  (dry) 1.4-1.65 

"     (moist) 1.9-2.05 

Sandstone 2.2-2.5 


ANALYSIS  OF  PAINT  MATERIALS 


349 


SPECIFIC  GRAVITY  OF  VARIOUS  MATERIALS  —  Continued 


Sapphire 3.95-4.02 

Serpentine 2.4-2.7 

Silicon  (cryst.) 2.49  (io.°) 

"       (graphitic) 2.0-2.5 

"       (amorphous) 2.00 

Silk  (raw) 1.56 

Silver  Chloride 5-56i 

"      Cyanide 3.95 

"      Nitrate 4.352(19.°) 

Slate 2.65-2.7 

Snow  (loose) 125 

Sodium  Acetate 1.4 

"       Bicarbonate 2.19-2.22 

"        Bromide 2.95-3.08 

"        Carbonate 

(anhyd.) 2.43-2.51 

"        Carbonate 

10  H2O 1446  (17.°) 

Chloride 2.1741  (2f°) 

"        Chromate 2.71  (16.°) 

"        Bichromate 2.52  (16.°) 

"       Hydroxid 2.13 

"       Nitrate 2.267  ¥ 

Nitrite 2.I57250 

Oxid 2.805 

"       Peroxid 2.805 

"        Phosphate 

Na2HP04i2H20  1.5235  (16.°) 
"       Potassium  Tar- 

trate 1.77 

Sulphate  (anhyd.)  2-671  V 

ioH2O..i.492(20.°) 
"        Sulphide  Na2S.  .  .2.471 
Sulphite  7H2O...  i.  561 
"        acid.  ...1.48 

Tartrate 1.794 

"       Tetraborate 

(Borax) i.694.17° 

"       Thiosulphate 

5H20 1.729(17.°) 

Tungstate 3.259  (17.5°) 

Spathic  Iron  Ore 3-7-3-9 

Stannous  Chloride  2H2O.  .2.71  (15.5°) 

Starch 1.53-1.56 

Stearic  Acid 8428  8,° 

Stearin 9245  (65.°) 

Steel 7.6-7.8 

Strontium  Chlorate 3.152 

Strontium  Nitrate 2.24-2.98 


Sugar  (cane) 1.588  (20.)  0 

Sulphur  nat 2.07 

"        amorph.  soft  ....  1.9556  (o.°) 

"       plastic  87 1.92 

"        monoclinic  S/3  . .  .1.958 

"        rhombic  Sa 2.05-2.07  (o°) 

Sulphur  Dioxid 2.2639 

Sulphuric  Acid  H2SO4. . .  .  1.8342  V 
Syenite 2.6-2.8 

Talc 2.7 

Tartaric  Acid 1.666-1.764 

Terpineol 9357  (20.°) 

Thymol  (3:2:1) 9941  (o.°) 

Titanium  Oxid  TiO2 3.75-4.25 

Toluene 866  2?° 

Toluidine 998-1.046 

Tungsten  Oxid  WO2: 

(brown) 12.11 

Tungsten  Oxid  WO3: 

(yellow) 7.16 

Urea 1.323 

Uric  Acid i  .855-1 .893 

Verdigris 1.9 

Wax,  Bees: 

Yellow  m.p.  62.-62. 5.  °C  .g6-.965 
White  m.  p.  63.-63.5°C.  .96-.96g 

Wax,  Japan: 

(m.  p.  53-5°-54-5°)  •  •   -992 

Wheat 7-8 

Wood  (see  table  on  page  351). 

Wool  (sheep)  air-dry 1.32 

Xylene  o 8932  (c.°) 

"       m 866  2T° 

"       p 8801  (o.°) 

Zinc  Acetate i .  84 

Blende  ZnS 4.03-4.07 

Carbonate 4.42-4.45 

Chloride 2.91  ?£ 

Oxid 5.78 

Sulphate  anhyd 3.6235  (15.°) 

"        7H2O 1.964 

Sulphide 3.98 


(All  temperatures,  unless  otherwise  noted,  are  given  in  Centigrade  degrees.) 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


SPECIFIC  GRAVITY  OF  THE  ELEMENTS 


Aluminium 

Antimony 

Argon 

Arsenic 

Barium 

Bismuth 

Boron 

Bromine 

Cadmium 

Caesium 

Calcium 

Carbon 

Cerium 

Chlorine : 

Chromium 

Cobalt 

Columbium  (Niobium). 

Copper 

Erbium 

Fluorine 

Gadolinium 

Gallium 

Germanium 

Glucinum  (Beryllium). 

Gold 

Helium 

Hydrogen 

Indium 

Iodine 

Iridium 

Iron 

Krypton 

Lanthanum 

Lead 

Lithium 

Magnesium 

Manganese 

Mercury 

Molybdenum 

Neodymium 

Neon 

Nickel.  . 


2.60 

6.62 

1.379  (Air-I) 

5-73 

9.80 

2.50 

3-15  (Air-I) 

8.64 

1.88 

8.64 

2.17 

3-53 

6.68 

2.49  (Air-I) 

6.50 

8.60 

7.20 

8.933 

4-77 

1.26  (Air-I) 

1.31 

5-95 

5-469 

i-93 
19.32 

.1363  (Air-I) 
.0696  (Air-I) 

7.12 

4-943 
22.42 

7.86 

2.818  (Air-I) 

6-1545 
"•37 
•59 

1.74 

7-39 

13-55 

8.60 


.674  (Air-I) 
8.90 


Nitrogen 96737 

Osmium 22.48 

Oxygen i.ioS3s(Air-I) 

Palladium 1 1 .40 

Phosphorus : 

(White) 1.83 

(Red) 2.20 

Platinum 21.50 

Potassium 87 

Praseodymium 6.4754 

Radium 

Rhodium 12.10 

Rubidium 1.52 

Ruthenium 12.26 

Samarium 7.7-7.8 

Scandium 

Selenium 4.8 

Silicon: 

(Cryst.) 2.39 

(Graphitic) 2.00 

(Amorph.) 2.35 

Silver 10.50 

Sodium 978 

Strontium 2.54 

Sulphur 2.07 

Tantalum 10.4 

Tellurium 6.25 

Terbium 

Thallium 11.85 

Thorium n.oo 

Thulium 

Tin 7.29 

Titanium 3-543 

Tungsten: 

(Wolframium) 19.1 

Uranium 18.7 

Vanadium 5.50 

Xenon 4.422  (Air-I) 

Ytterbium 

Yttrium 3.80 

Zinc 7.25 

Zirconium 4.15 


POUNDS  OF  OIL  REQUIRED  FOR  GRINDING  100  POUNDS  VARIOUS  DRY  PIGMENTS 
INTO  AVERAGE  PASTES  1 


Asbestine 32 

Barytes  (Nat.) 9 

Black,  Bone 50 

Black,  Drop 50 

Black,  Hydro  Gas  Carbon 88 

Black,  Lamp 78 

Blanc  Fixe 25 

Blue,  Chinese  or  Prussian 62 


Blue,  Ultramarine 28 

Brown,  Mineral 24 

Brown,  Vandyke 58 

China  Clay 28 

Dutch  Pink  (Quercitron  Lake) 28 

Graphite  (Plumbago),  90% 48 

Green,  Pure,  Light,  Chrome 21 

Green,  Pure,  Dark,  Chrome 28 


ANALYSIS  OF  PAINT  MATERIALS 


351 


Green,  25%  Color,  Light  Chrome.  18 

Green,  25%  Color,  Dark  Chrome.  20 

Green  Earth  (Terra  Verte) 32 

Green,  American,  Paris 23 

Green,  English  Paris 20 

Green.  Ultramarine 28 

Gypsum 22 

Lithopone 30-25 

Ochre  (American) . .   28 

Ochre  (French) 28 

Ochre,  Golden  (Pure) 30 

Red,  Indian  (Pure  98%) 20 

Red,  Tuscan 2q 

Red,  Venetian 23 

Red  Iron  Oxid,  Pure 28 

Red  Lead 10 

Sienna,  Raw  American 45 

Sienna,  Burnt  Italian 45 


Sienna,  Raw  Italian 52 

Silex 24 

Umber,  Burnt  American 36 

Umber,  Raw  American 38 

Umber,  Burnt  Turkey 47 

Umber,  Raw  Turkey 48 

Vermilion,  American  (Chrome  Red)  18 

Vermilion,  English  (Mercury) 14 

White  Lead  (Basic  Carbonate) ....  10 

White  Lead  (Basic  Sulphate) 1 1 

White,  Paris  (Whiting) 20 

Yellow,  Lemon,  Chrome. 28 

Yellow,  Med.,  Chrome 30 

Yellow,  Orange,  Chrome 20 

Yellow,  Dk.  Orange,  Chrome 18 

Zinc  Lead 12 

Zinc  Oxid  (American),  ordinary  . .  18 

Zinc  Oxid  (White  Seal) 20 


1  These  figures  are  approximately  correct.  For  instance,  lamp  black  is 
given  as  78  pounds.  There  are,  however,  some  lampblacks  which  require  as  much 
as  100  pounds,  and  others  which  require  as  low  as  70  pounds,  but  78  pounds  is  the 
exact  amount  for  commercially  pure  lampblack.  This  figure  means  that  100 
pounds  of  lampblack  will  require  78  pounds  (about  10  gallons)  of  oil  to  make 
a  stiff  paste. 


SPECIFIC  GRAVITY  OF  VARIOUS  WOODS 


Air  dry 

Fresh 

Acacia     

.&-     8c, 

7"J—  I    OO 

Alder      

.42-     68 

Apple  

.66-    84 

oc.—  i    26 

Ash  

.  C7—     04 

Birch            

CT—      77 

Box           

91—1   16 

I    20—  I    26 

Cedar  

•57     •  •  • 

Cherry  

76-    84 

i  05—1    18 

Ebony  

i  .  26     ... 

Elm         

56-    82 

78-1   18 

Fir               

27—     7; 

77—1    2? 

Mahogany  

.56-1  .06 

Maple               

S3-    81 

8?—  i  oc 

Mountain  Ash     

60-         8O 

87-1  n 

Oak         

60—  I    O3 

o?—  i   28 

Pear  

61—     73 

96—1    07 

Pine              

•2C—         6O 

Plum                

68-    90 

87-1    17 

Poplar 

2Q—          C.O 

Willow.  .  . 

AQ—         CO 

7O 

352 


CHEMISTRY  AND   TECHNOLOGY  OF  PAINTS 


TABLE  SHOWING  THE  COMPARISON  OF  THE  READINGS  OF  THERMOMETERS 


Celsius,  or  Centigrade  (C).     Reaumur  (R).     Fahrenheit  (F). 


C 

R 

F 

C 

R 

F 

-3° 

—  24.0 

—   22  .0 

23 

18.4 

73-4 

-  25 

—  2O.O 

-   13-0 

24 

19.  2 

75-2 

—  20 

—  16.0 

-      4.0 

25 

20.0 

77.0 

-   15 

—  12.  O 

+    5-o 

26 

20.8 

78.8 

-   10 

-    8.0 

14.0 

27 

21  .6 

80.6 

-    5 

-  4.0 

23.0 

28 

22.4 

82.4 

-    4 

-    3-2 

24.8 

29 

23-2 

84.2 

-    3 

-   2.4 

26.6 

3° 

24.0 

86.0 

—      2 

-    1.6 

28.4 

3i 

24.8 

87.8 

—      I 

-    0.8 

30.2 

32 

25.6 

89.6 

33 

26.4 

91.4 

Freezing  point  of  water. 

34 

27.  2 

93-2 

35 

28.0 

95-0 

o 

o.o 

32.0 

36 

28.8 

96.8 

i 

0.8 

33-8 

37 

29.6 

98.6 

2 

1.6 

35-6 

38 

3°-4 

100.4 

3 

2.4 

37-4 

39 

31.2 

IO2.2 

4 

3-2 

39-2 

40 

32.0 

IO4.O 

5 

4.0 

41  .0 

4i 

32.8 

105.8 

6 

4-8 

42.8 

42 

33-6 

107.6 

7 

5-6 

44-6 

43 

34-4 

109.4 

8 

6.4 

46.4 

44 

35-2 

III  .2 

9 

7-2 

48.2 

45 

36-0 

II3.0 

10 

8.0 

50.0 

50 

40.0 

122.0 

ii 

8.8 

51-8 

55 

44.0 

I3I.O 

12 

9.6 

53-6 

60 

48.0 

I4O.O 

13 

10.4 

55-4 

65       ' 

52.0 

149.0 

14 

II  .2 

57-2 

70 

56.0 

I58.0 

15 

12  .O 

59-o 

75 

60.0 

167.0 

16 

12.8 

60.8 

80 

64.0 

176.0 

17 

13-6 

62.6 

85 

68.0 

185.0 

18 

14.4 

64-4 

90 

72.0 

194.0 

iQ 

15-2 

66.2 

95 

76.0 

203.0 

20 

16.0 

68.0 

IOO 

80.0 

212  .O 

21 

16.8 

69.8 

22 

17.6 

71.6 

Boiling  point  of  water. 

Readings  on  one  scale  can  be  changed  into  another  by  the  following  formulae, 
in  which  t°  indicates  degrees  of  temperature: 


Reau.  to  Fahr. 


Reau.  to  Cent. 


V  R  =  f  C 
4 


Cent,  to  Fahr. 

^°C  +  320  =  ;°F 

Cent,  to  Reau. 

±e  c  =  e  R 

5 


Fahr.  to  Cent. 

=  /°C 


Fahr.  to  Reau. 

=  /°R 


ANALYSIS  OF  PAINT  MATERIALS 


353 


INTERNATIONAL  ATOMIC  WEIGHTS.     1913 


o 

=  16 

0 

=  16 

Aluminium  

....Al 

27-1 

Molybdenum  

Mo 

96-0 

Antimony  

....Sb 

I  2O  -2 

Neodymium  

Nd 

144-3 

Argon  

....A 

39-88 

Neon  

Ne 

2O-  2 

Arsenic  

....As 

74-96 

Nickel  

Ni 

58-68 

Barium  

....Ba 

137-37 

Niton  (radium  emanation)  . 

Nt 

222-4 

Bismuth  

....Bi 

208-0 

Nitrogen  

N 

I4-OI 

Boron  

...  .B 

II  -0 

Osmium  

()s 

190-9 

Bromine  

....Br 

79-92 

Oxygen  

0 

16.00 

Cadmium  

....Cd 

1  1  2  •  40 

Palladium  

Pd 

106-7 

Caesium  

....Cs 

I32-8I 

Phosphorus  

P 

31-04 

Calcium  

....Ca 

40-07 

Platinum  

Pt 

195-2 

Carbon  

....C 

12  -OO 

Potassium  

K 

39-10 

Cerium  

....Ce 

I40-2S 

Praseodymium  

Pr 

140-6 

Chlorine  

....a 

35-46 

Radium  

Ka 

226-4 

Chromium  

.  .  .  .  Cr 

52-0 

Rhodium  

Rh 

102-9 

Cobalt  

....  Co 

58^)7 

Rubidium  

Kb 

85-45 

Columbium  

....Cb 

93-5 

Ruthenium  

Rn 

101  •  7 

Copper  

....Cu 

63-57 

Samarium  

Sa 

150-4 

Dysprosium  

....Dy 

162-5 

Scandium  

Sr 

44-1 

Erbium  

.  .  .  .  Er 

167-7 

Selenium  

Se 

79-2 

Europium  

....Eu 

152-0 

Silicon  

Si 

28-3 

Fluorine  

....F 

19-0 

Silver  

.A« 

107-88 

Gadolinium  

....Gd 

157-3 

Sodium  

Na 

23-00 

Gallium  

.  .  .  .  Ga 

69-9 

Strontium  

Sr 

87-63 

Germanium  

.  .  .  .  Ge 

72-5 

Sulphur  

S 

32-07 

Glucinum  

....Gl 

9-1 

Tantalum.  .  

Ta 

181-5 

Gold  

....Au 

197-2 

Tellurium  

Te 

127-5 

Helium  

....He 

3-99 

Terbium  

Tb 

159-2 

Holmium  

....Ho 

163-5 

Thallium  

Tl 

204-0 

Hydrogen  

....H 

i  -008 

Thorium.  

Th 

232-4 

Indium  

....In 

114-8 

Thulium  

Tm 

168-5 

Iodine  

....I 

126-92 

Tin  

Sn 

119-0 

Iridium  

....Ir 

IQ3-I 

Titanium  

Tl 

48-1 

Iron  t  .  .  .  . 

....Fe 

55-84 

Tungsten  

W 

184-0 

Krypton  

....Kr 

82-92 

Uranium.  

U 

238-5 

Lanthanum  

....La 

139-0 

Vanadium  

V 

51-0 

Lead  

Pb 

207-10 

Xenon  

XP 

130-2 

Lithium  

....Li 

6-94 

Ytterbium(Neoytterbium)Yb 

172-0 

Lutecium  

....Lu 

174-0 

Yttrium  

Yt 

89-0 

Magnesium  

....Mg 

24-32 

Zinc  

7,n 

65-37 

Manganese  

Mn 

54-93 

Zirconium  

7,r 

90-6 

Mercury  

...Hg 

200-6 

PHOTOMICROGRAPHS 


6. 


8. 


NUMBER 

1.  Corroded  White  Lead. 

2.  Old  Process  White  Lead. 

3.  White  Lead  (New  Process). 

4.  Sublimed  White  Lead. 

5.  Standard  Zinc  Lead  White. 
Ozark  White. 
American  Zinc  Oxid. 
French  Green  Seal  Oxid. 

9.  Lithopone  (dry). 

10.  Lithopone  (ground  in  oil). 

11.  Litharge. 

12.  Litharge. 

13.  French  Orange  Mineral. 

14.  Red  Lead  (Photomicrograph 

of  paint  film  freshly  ap- 
plied, showing  separation  of 
the  pigment  from  the  oil)  . 

15.  Red  Lead  (Photomicrograph 

of  red  lead  applied  one  hour 
after  mixing,  showing  sepa- 
ration and  air  bells  en- 
cysted in  film). 

English  Venetian  Red. 

American  Venetian  Red. 

American  Hematite. 

Indian  Red. 

American  Burnt  Sienna. 

Prince's  Metallic. 

Ordinary  American  Washed 
Ochre. 

American  Washed  Ochre. 

J.  F.  L.  S.  Ochre. 

25.  Ultramarine  Blue. 

26.  Ultramarine  Blue  (ground  in 

oil). 

27.  Artificial  Cobalt  Blue. 

28.  Lampblack. 


r6. 

17- 

18. 
19. 

20. 
21. 
22. 


PAGE 

NU3 

29 

29. 

3° 

30. 

31 

31- 

36 

32- 

38 

33- 

40 

34- 

43 

35- 

44 

36. 

47 

37- 

48 

38. 

54 

39- 

55 

40. 

57 

41. 

42. 

43- 

44. 

58 

45- 

46. 

47- 
,18 

40. 
49- 

59 

5°- 

64 

5i- 

65 

52- 

66 

53- 

66 

54- 

72 

55- 

75 

56. 

57- 

79 

58. 

80 

59- 

81 

60. 

85 

61. 

62. 

85 

63- 

88 

64. 

99 

65- 

Carbon  Black. 

Natural  Graphite. 

Natural  Graphite. 

Artificial  Graphite. 

Artificial  Graphite. 

Fine  Charcoal. 

Charcoal  Black. 

Vine  Black. 

Wood  Pulp  Black. 

Drop  Black. 

Drop  Black. 

Barytes. 

Barytes,  American. 

Blanc  Fixe. 

Blanc  Fixe. 

Barium  Carbonate. 

Silica  or  Silex. 

Silica. 

Silica. 

Infusorial  Earth. 

Diatoms. 

Diatoms. 

Clay. 

China  Clay. 

Colloidal  Clay. 

Asbestine. 

Whiting. 

Gilder's  Whiting. 

Calcium  Carbonate,  artificial. 

Talc  (Soapstone). 

59.  Basic  Magnesium  Carbonate. 

60.  Alumina  Hydrate. 

61.  American  Gypsum. 

62.  American  Gypsum. 
American  Terra  Alba. 

64.   Calcium  Sulphate  (Gypsum). 
French  Terra  Alba. 


PAGE 

IOO 
IOI 
IO2 
103 
104 
105 
105 
1  06 
lO/ 
1  08 
1  08 

"3 
"5 

117 

120 
122 
123 
123 
124 
126 
127 
127 
128 
I29 
129 
130 


132 
132 
133 
133 
I36 
I36 
136 
136 
137 


356 


NUMBER  PAGE 

66.  Terra  Alba  (French  Gypsum).   137 

67.  Calcium  Sulphate.  137 

68.  Precipitated     Calcium     Sul- 

phate. 137 

69.  Photomicrograph  of  Portland 

cement  floor  composed  of  2 
parts  sand  and  i  part 
cement.  147 

70.  Highly  magnified  view  of  a 


NUMBER  PAGE 

fine     crack     in     Portland 

cement  construction.  148 

71.  Olive  green   fungus  growing 

on  paint.  284 

72.  Penicilium  Crustaceum.  285 

73.  Aspergillus  Niger.  285 

74.  Aspergillus  Niger.  286 

75.  Aspergillus  Flavus.  286 

76.  Cladosphorium  Herbarum.  287 


INDEX 


Acetylene  black,  as  black  toner,  108 
Acid  value,  det.  in  oils  and  resins,  336 
Adulteration  of  white  lead,  16,  17 
Alabaster,  use  in  making  gypsum,  137 
Alum  salts,   use  in  fireproofing  wood, 

129 
Anti-fouling  paints,  preparation  of,  144, 

145 

Antwerp  blue  —  see  Prussian  blue 
Asbestine,  analysis  of,  130,  312 

composition,  128 

fireproof  paint,  use  in,  128 

shingle  stain,  use  in,  156 
Asbestos,  fireproof  paints,  use  in,   128 

identification,  130 
Aspergillus  Flavus,  286 
Aspergillus  Niger,  286 
Asphalts,  influence  of  sunlight  on,  261, 
262 

chemical  composition  of,  262 

Bancroft  —  see  lithopone 
Barium  carbonate,  121 
analysis  of,  315 
manufacture  of,  122 
paints,  value  in,  122 
versus  Witherite,  122 
Barium  sulph.,  artificial  —  see  blanc  fixe 

natural  —  see  barytes 
Barytes,  112 

analysis  of,  312,  314 

bleaching  of,  116 

bulking  of,  in  oil  and  paint,  115 

chirt  rock  in,  116 

exposure  tests  of  paints  containing, 

114 
filler,  value  as,  113 

versus  other  fillers,  115 
occurrence,  115 
para  red,  use  of  with,  113 


treatment  of,  116 

wearing  qualities  of  paints  contain- 
ing, 112,  114 
Battleship  gray,  blanc  fixe,  use  of,  in, 

118 

exposure  tests  of,  on  "Panther,"  119 
manufacture  of,  119 
Beckton  white  —  see  lithopone 
Benzine,  238 

and   condensation   of   water  due   to 

evaporation  of,  239 
distillation  of,  241 
use  in  paints,  238 
Benzol,    composition,    production    and 

cost  of,  243 
crude,  243 
properties  of,  244 
use  in  black  paints,    244 
use  in  finishing  coats  (objection  to), 

244 

use  to  prevent  livering,  244 
use  in  priming  paints,  244 
Benzol  black,  107 

behavior  in  oil,  108 

Bitumens,  chemical  composition  of,  262 
exposure  tests  of,  264 
paints,  deterioration  of,  264 
sunlight,  effect  of,  on,  261,  262 
Black  lead,  —  see  graphite 
Black  pigments,  97 
analysis  of,  309 

Prussian  blue  in  detection  of,  309 
varieties  of,  97 
acetylene,  108 
benzol,  107,  108 
bone,  97 
carbon,  100 
color  in  varnish,  98 
Black  pigments,  varieties  of, 
drop,  106,  107 


358 


INDEX 


Black  pigments,  varieties  of, 
ivory,  106 
lamp,  98,  99 
mineral,  109 
sugar  house,  97 
toner,  97 
vine,  104 
Blanc  fixe,  116 
analysis  of,  310 
consumption  of,  in  U.  S.,  120 
manufacture  of,  116,  121 
salt  water,  effect  of,  on  paints  con- 
taining, 120 

use  in  enamels,  117,  118 
"     "  lakes,  117,  118 
"    "  linoleum,  120 
"    "  oil  cloth,  1 20 
"    "  paints,  as  reinforcing  pigment, 

118 

"    "  paper,  116,  117 
"     "  printing  ink,  120 
Bleaching,  of  oils,  171,  172 
Blood  stone  —  see  iron  oxids 
Blown  oils,  analysis  of,  1 79 
Blue  lead,  composition  and  properties,  61 

pigments,  84 
Boiled  linseed  oil,  specifications  for,  174, 

175 

Bone  black,  97 

Branding,  of  white  lead,  16,  17 
Branding  of  mixed  paint,  17 
Breninig  —  see  silex 
Bromide  test,  340 
Bronze  blue  —  see  Prussian  blue 
Brooke  —  see  soya  beans 
Brown  pigments,  71 
Burnt  ochre,  74 
Burnt  sienna,  71 

American,  71,  72 
Italian,  72,  73 
Burnt  umber,  63 

Calcium  carbonate  —  see  whiting 
resinate,  formation   of,    in    concrete 

floors,  147 
as    protection    for   concrete    from 

machinery  oils,  147 
sulphate  —  see  gypsum 


Carbon  black,  properties,  100 
dioxid,  effect  of,  on  white  pigments, 

140 
paints,  141 

wearing  qualities  of,  141 
Cassel  brown  —  see  vandyke  brown 
Cement  paints  —  see  concrete  paints 
Cement,  Portland,  use  of,  in  paints,  146, 

149 

Chalk  —  see  whiting. 
Charcoal,  alkalinity  in,  104 
manufacture  of,  104 
paint  pigment,   use  as,    104 
preservative     coating      from,      and 

litharge,  104 
saponification  of,  paints  in  presence 

of  moisture,  105 
uses  in  oil  cloth  and  coated  leather, 

105 

Charlton  white  —  see  lithopone 
China  base  oil,  185 
Chinese  blue  —  see  Prussian  blue 
wood  oil,  1 80 

acidity  of,  effect  in  enamels,  185, 

1 86 
adulteration  of,  184 

detection  of,  187 
analysis  of,  182 
calcium  oleate  in,  182 
Canton,  181 

chemical  composition  of,  183 
constants  of,  182 
drying  of,  180,  181 
gelatinization,  181,  185 
Hankow,  181 
heating  of,  181,  184 
odor  of,  means  of  detection,  182, 185 
paints,  181 

enamel,  182 

polymerization  of,  181,  185 
raw,  in  flat  wall  paints,  186,  187 
rosin  varnish,  187 
specifications  for,  190 
uses,  183,  184 

in  baking  enamels,  187 
in  cement  floor  paints,  187 
waterproof  qualities  of,  183 
wearing  qualities  of,  183 


INDEX 


359 


Chirt  rock  —  see  barytes 
Chlorophyll  in  linseed  oil,  169 
Chrome  green,  analysis  of,  304 
composition  of,  92 
permanence  of,  93 
Chrome  yellow,  analysis  of,  303 
composition  of,  82 
permanent  of,  82 
preparation  of,  81 
Chromium  oxid,  93 
manufacture  of,  94 
use  in  delicate  greens,  94 
Cinnabar,  66 
Clay,  127 

analysis  of,  128,  312 
presence  of,  in  ochres  and  siennas,  127 
uses,  in  paints  to  prevent  settling,  127 
in  cheap  barrel  and  paste  paints, 

127 

water  in,  127 
wearing  qualities  of  paint  containing, 

127 

Coal,  use  of,  in  paints,  106 
Coarse  paints,  value  as  priming  coats,  259 
Cobalt  blue,  87,  88 

determination  of,  in  paints,  88 
distinction  from  lithopone,  88 
permanence  of,  88 
strength  of,  88 
with  driers,  89 
Cobalt  driers,  247 

amount  required  to  dry  oil,  249 
incorporating,  in  oils,  252 
linoleate,  251 
liquid,  252 
oleate,  251 
oleoresinate,  251 
resinate,  250 
tungate,  251 

use  with  soya  bean  oil,  200 
Cobalt  salts,  247 
acetate,  252 
oxid,  252 
oxidation  of,  248 
Combining  mediums,  254 

rosin-mixing  varnishes  as,  254 
rubber  solutions  as,  254 
water  as,  254 


Commonwealth  white  —  see  whiting 
Complex  ore,  low  grade,  37 
Concrete  floors,  abrasion  and  dusting 
of,  146 

acids,  use  of,  in  painting  of,  146 

calcium  resinate  as  protection  for,  147 

lime,  free,  in,  147 

machinery  oils,  effect  of,  on,  147 

resin  acids  for  coating,  147 

zinc  sulphate,  use  in,  148 
Concrete  paints,  146 

consumption  of,  148 

use  of  Chinese  wood  oil  and  copals  in, 

147,  148 
"Cooler,"  18 
Copper,  anti-fouling  paints,  145 

green,  96 
Corn  oil,  214 

analytical  constants,  215,  216 

drying  of,  235 

treatment  of,  215 

uses,  214 

versus  soya  bean  oil,  215 
Corrosion,    electrolytic,    of    structural 
steel,  276 

electrolytic,  at  anode,  276,  277,  278 

paint  vehicles   as  protective  agents 

against,  266 
Creosote,  use  in  shingle  stain,  156 

Damar  enamels,  151 
gum,  acid  value  of,  151 
varnish,  preparation  of,  152 

Damp-resisting  paints,  149,  150 

adhesion  of,  to  brick  and  mortar,  149, 

150 
use  of  Chinese  wood  oil  and  linseed 

oil  in,  150 
Diatoms,  nature  of,  and  composition, 

126 

use  in  lakes  and  paints,  126 
Dickens's  "Bright  Star  in  the  East,"  31 
Drier,  cobalt,  247 
Japan,  163 

Japanners'  Prussian  brown  as,  163 
lead  sulphate  as,  163 
lime  oil,  163 
litharge  as,  162 


INDEX 


Drier,  manganese  salts  as,  162,  163 

Prussian  blue  as,  163 

red  lead  as,  162 

zinc  sulphate  as,  163 
"Drifts,"  19 
Drop  black,  106,  107 
Durex  white  —  see  barium  carbonate 

East  Indian  red,  65 

Eibner   and   Muggenthaler  —  see   bro- 
mide test 

Emulsifiers,  256,  257 
Enamel  oil,  typical  analysis  of,  1 79 
Enamel  paints,  composition,  151 

damar  type  of,  151 

definitions  of,  150 

lithopone,   wood  oil,  rosin  type 
of,  152 

stand  oil  type  of,  152 
Erythrophyll  in  linseed  oil,  171 
Exposure  tests  of  paint  vehicles,  266, 

272,  273 
Extenders  —  see  fillers 

Farnau  —  see  lithopone 

Ferric    oxid    paints  —  see    iron    oxid 

paints 

Ferric  oxids  —  see  iron  oxids 
Fillers,  as  adulterants,  1 1 1 ,  112 

barytes  as,  113 

battleship  gray,  use  in,  in 

clay,  use  of,  as,  127 

inert,  value  in  paints,  no 

occurrence  in  pigments,  in,  127 

principal,  value  of,  112 

wearing  qualities  of  paints  as  affected 

by,  141 
Fine  grinding,  259 

for  finishing  coats,  259 

and  rubbing  of  varnishes,  260 
Fire  proof  paints,  128,  129 

alum  salts,  use  in,  129 

for  shingles,  130 

Fish  oil,  analytical  constants  of  men- 
haden, 207 

analytical  constants  of  varieties  of, 
204 

drying  of,  208 


herring  oil,  210 
pseudo  versus  genuine,  203 
red  lead,  use  of,  in,  207 
specifications  for,  209 
treatment  of,  205 
Fish  oil,  use  of,  in  baking  japans,  207 

in  enamel  leather  and  printing 

ink,  206 

in  exterior  paints,  205 
in  paints,  204 
on  seacoast,  207 
in  smokestack  paints,  207,  208 
in  waterproof  paints,  207 
Floor  paints  —  see  concrete  paints 
Foots,  in  linseed  oil,  171 
Fuller's  earth,  126,  127 
Fungi,  definition  of,  284 
fungicides,  use  of,  for,  286 
growth  of,  on  paints,  284 
varieties  of,  286 

Gilder's  white  —  see  whiting 
Glycerides,  influence  of  sunlight  on,  263 
Gmelin  —  see  ultramarine  blue 
Graphite,  Acheson,  102 

analysis  of,  310 

behavior  of,  in  linseed  oil  with  other 
pigments,  101 

brown,  102 

exposure  of,  and  iron  oxid,  102 

fillers  in,  use  of,  103 

film,  adaptability  for  repainting,  103 

green,  102 

paint  film,  103 

paints,  141 

properties  of,  101 

red,  1 02 
Green  aniline  lakes,  95 

chrome,  92,  304 
Grinding,  fine,  259 

paste,  18,  19 

surfaces  of  mills,  19 
Guinet  —  see  ultramarine  blue 
Gypsum,  alabaster  as  source  of,  137 

analysis  of,  139,  311 

calcium  chloride  as  source  of,  138 

composition  and  occurrence  of,  135 

free  lime  in,  136 


INDEX 


361 


Gypsum,  hydra tion  of,  137 
presence  of,  in  Venetian  red,  138 
use  of,  in  freight  car  color,  138 

as  paint  filler,  136 
water  in,  136 

Harrison  Red,  69 
Helio  Fast  Red,  69,  70 
Hematite  —  see  iron  oxids 
Hermann  —  see  ultramarine  blue,  85 
Herring  oil,  210 

acidity  of,  211 

drying  of,  214 

treatment  of,  213,  214 
Hough  process  —  see  pine  oil,  229 
Huhlmann  —  see  ultramarine  blue,  85 
Hygiene,  painters',  281 
Hypha  —  see  fungi,  284 
Hypochlorite  of  lime,  in  shingle  stain, 
156 

Indian  red  —  see  iron  oxids,  64 
Infusorial  earth,  122 

composition  and  properties,  125 

use  of,  in  paints,  126 
Iodine  value,  det.  of,  of  oils,  337 
Iron  —  see  corrosion 
Iron  oxids,  analysis  of,  299 

bloodstone,  65 

East  Indian  red,  65 

hematite,  65 

Indian  red,  64 

manufacture  of,  63 

paints,  141,  142,  144 

Persian,  63,  65 

protective  pigments,  62 

rouge,  watch  case,  66 

rubber  pigments,  62 

shingle  stain,  156 

Venetian  reds,  63,  64 
Ivory  black,  coach  color,  106 

extract  of,  106 

properties,  106 

Japanners'  Prussian  brown,  163 
Jersey  lily  white  —  see  lithopone 

Kaolin,  127,  128  —  see  clay 


Kaolinite,  128 

Kauri  dust,  use  of,  in  japan  driers,  163 

Kieselguhr,  126 

Koettig  —  see  ultramarine  blue,  86 

Lake  base  —  see  blanc  fixe 

Lampblack,  98,  99 

Lapis  lazuli,  84 

"Lead,"  meaning  of,  19 

Lead,  oxids,  53 

peroxid,  det.  of,  in  red  lead,  298 
sulphate,  basic,  anal,  of,  290,  26,  35, 

38,39 
drier,  163 

Les  Valees  —  see  soya  beans,  194 
Leverkus  —  see  ultramarine  blue,  86 
Leverkusen  —  see  ultramarine  blue,  86 
Leykauf,  see  ultramarine  blue,  87 
Leykauf  and  Zeltner  —  see  ultramarine 

blue,  86 

Liebermann,  Storch  reaction,  330 
Light  —  see  sunlight 
"Light  wood  "  —  see  pine  oil,  231 
Lime  oil,  163 
Linseed  oil,  adulteration  of,  159 

analysis,  typical  of,  1 74 

analytical  constants  of,  158,  161 

Baltic,  158 

bleaching  of,  171 

blown,  typical  analysis  of,  179 

boiled,  specifications  for,  174,  175 

"breathing  of,"  168,  169 

Calcutta,  159 

carbon  dioxid  from,  168,  169 

coloring  matter  in,  169,  171 

deterioration  of,  173 

driers  and  drying  of,  162,  163 

extraction  of,  160 

film,  porosity  of,  164,  166 

new  process,  160 

N.  American,  158 

paints,  164,  165 

patent  leather,  use  of,  in,  165 

reactions  of,  with  pigments  in  can, 

173 

refining  of,  169 
saponification  of,  164 
specifications  for,  174,  175 


362 


INDEX 


Linseed  oil,  treating  of,  165 

waterproof  qualities  of,  164,  165 
Liquid  paint,  23 
Litharge,  as  drier,  162 

cement,  56 

flake,  54 

livering  of,  in  mixed  paints,  53 

manufacture  of,  53 

testing  of,  53 

use,  in  black  paints,  53 

in  preservative  paints,  53 
Lithol  red,  70 
Lithopone,  26,  46 

analysis  of,  296 

barium  sulphate  in,  48 

composition  of,  46 

darkening  of,  by  sunlight,  49 

enamels,  152 

manufacture  of,  46,  47 

paint  pigment,  49 

yellow  color  of,  cause,  49 

zinc  oxid  in,  48,  51 
Long  oil,  177,  178 

Maize  oil  —  see  corn  oil 
Manganese  salts,  as  driers,  162,  163 
Marble  dust,  as  filler,  130,  133,  134 
Marble  oil,  176 
Mercury  sulphide,  66 

analysis  of,  302 
Mildew,  formation  of,  284 
Mills,  for  grinding  paints,  19,  20 
Milori  blue  —  see  Prussian  blue 
Mineral  black,  composition  and  prop- 
erties, 109 
Mixed  paints,  analysis  of,  324 

anti-fouling,  144,  145 

benzol,  in,  244 

bleaching  of  white,  173 

branding  of,  17 

carbon,  141 

concrete,  146 

consumption  of,  14,  143 

covering  qualities  of,  141 

damp-resisting,  149,  150 

distribution  of,  in  factory,  20 

enamel,  150,  151,  152,  153 

ferric  oxid,  141,  142 


fillers  in,  14,  16,  141 

fire-resisting,  155 

flat,  wall,  154 

floor,  155 

graphite,  141 

guarantees  of  manufacturers,  143 

iron  oxid,  144 

manufacture  6f,  18 

origin  of,  13 

Portland  cement,  146,  149 

primer  on  wood,  143 

shingle,  155 

storage  of,  20,  21,  22 

tinting,  tanks  for,  locating,  20 

water  in,  13,  17 

wearing  qualities  of,  effect  of  fillers 

on, 141 

white,  exposure  tests  of,  140 
white  lead,  effect  of  rain  water  and 

carbon  dioxid  on,  140 
zinc  vs.  white  lead,  140,  142 
Mixers,  liquid,  18 
for  mixed  paint,  20 

Naphtha  —  see  benzine 
Nitroparatoluidine  —  see  Helio  Fast  Red 

O'Brien  —  see  lithopone,  49 
Ochre,  American  yellow,  78 

burnt,  74 

clay  in,  127 

cream,  79 

French,  brands  of,  79,  80 

golden,  79 

gray,  79 

green,  80 

white,  79 
Oils,  acid  value,  det.  of,  336 

analysis  of,  334 

blown,  typical  analysis  of,  179 

bromide  test  for,  340 

Chinese  wood,  180 

corn,  214 

enamel,  typical  analysis  of,  179 

fish,  203 

herring,  210 

iodine  value,  det.  of,  337 

Japanese  wood,  180 


INDEX 


363 


Oils,  Japanners'  Prussian  brown,  178 

linseed,  158 

long,  177 

maize,  215 

marble,  176 

menhaden,  203 

pine,  228 

short,  177 

soya  bean,  192 

specific  gravity,  det.  of,  334 

stand,  176 

Tung,  1 80 

Turpentine,  217 
Oleum  white  —  see  lithopone 
Orange  mineral  —  see  red  lead 
Orr  —  see  lithopone,  46 
Orr's  white  —  see  lithopone 
Ozark  white,  26,  39 

composition  and  manufactureof,  40,41 

Paint,  bactericidal  action  of,  284 

bitumen,  exposure  tests  of,  264 

coarse,  as  priming  coats,  259 

fillers,  use  in,  14 

fine,  as  finishing  coats,  259 

floor,  19 

fungi  in,  284 

mildew  on,  284 

mixed  —  see  mixed  paints 

paste,  manufacture  of,  18,  19 

pigments,  analysis  of,  317 

sunlight,  influence  of,  261 

varnish,  19 

Painters'  hygiene,  281,  282 
"  Panther,"  exposure  test  of  Battleship 

.    gray  on,  119 
Paranitraniline  red,  67 

barytes,  use  of,  in,  113 

bleeding  of,  69 

manufacture  of,  68 

reactions,  67 

permanence  of,  68 

uses  of,  69 
Paris  blue  —  see  Prussian  blue 

white  —  see  whiting 
Paste  grinding,  18,  19,  23 
advantages  of,  25 

mills,  23,  24,  25 


Patent  leather,  use  of  linseed  oil  in,  165 

Penecilium  crustaceum,  286 

"Periphery,"  19 

Permanent  white  —  see  blanc  fixe 

Persian  oxids,  63,  65 

Pigments,  analysis  of,  317 

reinforcing,  no 
Pine  oil,  analysis  of,  237 

distillation  of,  fractional,  237 
extraction  of,  228,  230 
bath  process,  231 
destruct.-distill.  process,  230 
Hough  process,  229 
formation  of,  233 
light  wood  as  source  of,  231 
long  leaf,  232 

relation  to  turpentine  and  rosin,  232 
solvent  properties  of,  234 
terpineol  in,  233 
use  of,  in  paints,  234,  235 
water  in,  detection  of,  234,  235,  332 
Ponolith  —  see  lithopone 
Potassium  dichromate,   use  in  shingle 

stains,  156 

Priming  coat  for  wood,  143 
Princess  metallic,  71,  74 
composition  of,  76 
mining  and  milling  of,  75 
paints,  wearing  qualities  of,  144 
properties  and  uses  of,  75 
Princess  mineral  brown,  74 
Prussian  blue,  analysis  of,  91,  306 

composition  and  manufacture  of, 

89 

properties  of  and  uses,  90,  91 
varieties  of,  90 

Prussian  brown,  Japanners,  as  drier,  163 
Prussian  brown  oil,  Japanners,  178 
Putty,  whiting,  132 

Quartz,  123 

Quicksilver  vermilion,  66 

Raw  sienna,  78 

Red  lead,  analysis  of,  298 

drier,  use  of,  for  oil,  162 

Dutch  boy,  56 

field  test  vs.  laboratory  test,  60 


INDEX 


Red  lead,  fillers,  use  of,  with,  59 
graphite,  use  of,  with,  59 
litharge  in,  54 
manufacture  of,  54 

nitrite  of  soda  process,  55 
semi-paste,  56 
saponifying  action  of,  56 
specification  for  dry,  56 
use   as   priming   coat   for   steel, 

IS,  54,  56 
disadvantages,  57 
in  linseed  oil,  54 
pigments,  62 

Reinforcing  pigments,  no 
Rhizopus  Nigricans,  286 
Rosin,  analysis  of,  326 
oils,  330 
spirit,  331 

Rouge,  watch  case,  66 
Rubber  solutions,  as  combining  media, 

254 
Rubbing  of  varnishes,  259 

Saponification  value,   det.  of,   of   oils, 

335 

Shingle  stain  and  paint,  155,  156 
Ships'  bottom  paints,  144 
"Short  oil,"  177,  178 
Sienna,  burnt,  American,  71,  72 

Italian,  72,  73 
raw,  78 
clay  in,  127 
Silex  —  see  silica 
Silex  Lead  Co.  —  see  silica,  123 
Silica,  analysis  of,  312 
detection  of,  124 

in  blanc  fixe,  310 
exposure  tests  of  paints,  containing, 

124 

hydration  of,  125 
quartz,  125 
tooth,  124 
use  of,  as  filler,  125 
Silicate  of  alumina  —  see  clay 

of  soda,  early  use  in  paints,  13 
Solvent  naphtha,  246 
Soya  bean,  analysis  of  varieties  of,  195 
in  Far  East,  193 


plant,  as  crop  for  unproductive  soil 
196,  197 

products  from,  194 
Soya  bean  oil,  192 

analytical  constants  of,  197,  199 

blown,  constants  of,  200 

detection  of,  201 

extraction  of,  in  laboratory,  195 

introduction  of,  192 

properties  of,  196 

testing  of,  199 

use  in  baking  japans,  199 

in     linoleum,     oil     cloth     and 

enamels,  201 
of  cobalt  drier  with,  200 
of  tungate  driers  with,  201 
Soya  bean  oil,  varieties  of,  193 

wearing  qualities  of,  200 
Spanish  white  —  see  whiting 
Specifications  for  Chinese  wood  oil,  190 

for  fish  oil,  209 

for  linseed  oil,  174,  175 

for  turpentine,  223,  225 
Specific  gravity,  det.  of,  of  oils,  334 
Stand  oil,  176 

driers  in,  177 

enamels,  152,  153 

origin  of,  176 

preparation  of,  177 

wearing  qualities  of,  177,  178 
Steel  blue  —  see  Prussian  blue 
Stove  polish  —  see  graphite 
Sublimed  white  lead,  26,  35 

analysis  of,  290 

composition  of,  35,  36,  37,  39 

consumption  of,  35 

exposure  tests  of,  39 

manufacture  of,  35 

properties,  35,  36,  38,  39 

sulphur  gases,  effect  of,  on,  36 

use  in  marine  paints,  37 

use  in  mixed  paints,  38,  39 
Sugar  house  black,  97 
Sulphate  of  lead,  34 

Sunlight,    influence    on    asphalts    and 
bitumens,  261,  262 

influence  on  glycerides,  263 

influence  on  lithopone,  49 


INDEX 


365 


Sunlight,  influence  on  paints  and  var- 
nishes, 261 
influence  on  pigments,  264,  265 

Teeple  —  see  pine  oil,  232 

Terpine  hydrate,  from  pine  oil,  233 

Terpineol,  in  pine  oil,  233 

Terre  verte,  80 

Tessaert  —  see  ultramarine  blue,  85 

Thompson   "breaking"   of  linseed  oil, 

172 

Tiemann  and  Schmidt  method,  233 
Tinting  tanks,  in  mixed  paint  manu- 
facture, 20 

Toch,  H.  M.  —  see  Lake  base,  116 
Tockolith,  149 
Toluol,  245 
"Tooth" — see  silica,  124 

in  priming  coats,  259 
Tungate  (Tox),  manufacture  of,  208 

use  with  soya  bean  oil,  201 

use  with  fish  oil,  208 
Tung  oil  —  see  Chinese  wood  oil 
Turpentine,  adulteration  of,  detection 
of,  220 

American  vs.  Russian,  218 

analysis  of,  218,  219,  224 

composition  of,  217 

extraction  of,  217 

properties  of,  218 

rosin  from,  217 

specifications  for,  223,  225 

substitutes,  240,  243 

use,  as  paint  thinner,  217,  220 

versus  petroleum  thinners,  221 

wood,  composition  of,  218,  222 
manufacture,  221,  222 
uses,  223 
Twitchell  method,  for  rosin,  327 

Ultramarine,  ashes,  84 
Ultramarine  blue,  analysis  of,  307 

composition  of,  86 

discovery  of,  84 

manufacture  of,  85 
natural,  84 

permanence  of,  87 

prices  of,  86 


resistance  to  alum,  87 

various  shades  of,  87 
purple,  87 
red,  87 

Vandyke  brown,  71,  76 

Vanquelin  —  see  ultramarine  blue,  85 

Varnish  paints,  19 

rubbing  of,  260 

Venetian  reds,  composition  and  manu- 
facture, 63,  64 
Vermilion,  Chinese,  66 

English,  66 

permanent,  66,  70 

Trieste,  67 

Veronese  green  —  see  chromium  oxid 
Verte  antique,  96 
Vine  black,  105 

Wall  paints,  flat,  manufacture  of,  154 

raw  Chinese  wood  oil  in,  187 
Water,  in  paints,  amount  permissible, 

255,  257 
analysis  of,  332 
detection  of,  258 
emulsifiers  for,  256,  257 
value  of,  254,  256 
rain,  effects  of,  on  white  lead  paint, 

140 

Wearing  qualities  of  paint  and  combina- 
tions of  pigments,  28 
West  —  see  iron  oxids,  64 
White  filler,  134 
White  lead,  28 

adulteration  of,  16,  17 
analysis  of,  288 
branding  of,  16,  17 
chalking  of,  32,  33,  140 
composition  of,  28,  30 
covering  quality  of,  33 
Dutch  process,  29 
exposure  tests  of,  140 
fillers  with,  effect  of,  33,  34 
paint,  oil  in,  31 

volatiles  in,  32 
paste,  oil  in,  31 
primer,  on  wood,  29 
quick  process,  29 


366 


INDEX 


White  lead,  soap,  formation  of,  30 

sublimed,  26,  35,  38,  39 
analysis  of,  296 

sulphur  gases,  effect  of,  on,  33 

toxicity  of,  30,  31 

varieties  of,  26 

versus  zinc  oxid,  142 

weathering  of,  32,  33 
White  mineral  primer  —  see  whiting 
White  pigments,  26,  27,  28 

versus  other  fillers,  134 
Whiting,  acidity  in  paints,  corrected  by, 

131 

analysis  of,  311 

by-product,  134 

durability  of,  in  oil,  132 

filler,  132,  133,  134 

manufacture  of,  130,  131 

putty,  132 

white  mineral  primer,  134 
Williams  —  see  anti-fouling  paints,  144 
Witherite,  122 

Wolf  and  Scholze  method,  for  rosin,  329 
Wood  oil,  rosin  enamels,  152 
Wood  turpentine,  composition,  222 

manufacture  of,  222 

uses  in  paints,  223 

Xantophyll,  in  linseed  oil,  169 
Xylol,  246 


Yellow,  chrome,  81,  82,  303 
ochre,  78 
oxid  80 
pigments,  78 

Zinc  chromate,  as  rust  preventive,  82 
green,  composition,  properties,  uses, 

95 
lead,  26 

analysis  of,  291 
complex  ore,  37 
composition  of,  38 
manufacture  of,  3.7 
white,  standard,  37 
Mineral  Point,  26 
oxid,  41 

analysis  of,  293 
brands,  26,  43    ' 
chalking  of,  44 
consumption  of,  4 1 
oxidation  of,  in  oil,  42 

vs.  other  driers,  42,  43 
paint,  13 

exposure  test  of,  140 
vs.  white  lead  paint,  142 
paste,  amount  of  oil  in,  41 
sulphur  gases,  effect  of,  on,  41 
zinc  sulphate  in,  44,  45 
sulphate,  as  drier,  163 
Zinox,  45 


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